Physical conditions in this Israeli-run prison camp have improved considerably in the last few months, but to its 5,400 Palestinian and Lebanese inhabitants it remains a harsh place of isolation where they say they are being held "hostage" to political processes controlled by others.

Hastily established in the first weeks after Israel's invasion of Lebanon last June, the camp is situated on a high mountain plateau about five miles west of the southern Lebanese city of Nabatiyah. At one time or another, most of the about 11,000 men who have been captured or otherwise detained by the Israelis since the invasion have spent time behind its steel and barbed-wire fences.

This week the Israeli Army allowed two reporters to enter the camp, the first visit by journalists here in two months. In answer to a request to speak to prisoners, the Army also agreed to an interview with the head of the prisoners' committee, a Palestine Liberation Organization colonel, but requested that his name not be used.

The picture that emerged--from the comments of Israeli authorities, the prisoner and officials of the International Committee of the Red Cross who visit Ansar almost daily--is of a prison camp where the basic necessities of life are provided and where there is no systematic abuse of the prisoners.

"Life here has gone through stages," said the prisoners' committee head, a 39-year-old native of Bethlehem who was brought to Ansar about three months ago after being held elsewhere in Lebanon. "At first, this place was hell. Then there were improvements."

But even with the physical improvements--the installation of kerosene heaters in the prisoners' tents, a doubling of the daily cigarette ration to 10 per man, the provision of English- and Arabic-language newspapers published in Israel--it is a bleak existence where the only regular daily activity is the 8 a.m. count of the prisoners by the Israeli guards. It is made worse by the uncertainty of the prisoners' captivity, the fates of their families and their own destiny if and when Israel agrees to withdraw from Lebanon.

"I will not say that this is Auschwitz, but it is a concentration camp," the prisoner said in the presence of Israeli officials.

"The basic problem is that there are more than 5,400 detainees here . . . young people and old people, some mentally retarded from birth, some who have lost their memories. We believe we are being misused for political pressure. We have no lawyer, we don't see our families . . .

"It's not the bread, the food; it's our families, it's the future, it's our basic human rights."

Eventually, he said, he believes that as part of a troop withdrawal agreement most of the prisoners will be exchanged for the eight Israeli soldiers held by the Syrians and PLO, and expelled from Lebanon. Meanwhile, the negotiations between Israel and Lebanon that likely will decide their futures go on, and the Ansar prisoners pass the cold, wet days of the Lebanese winter in their Israeli Army tents, uncertain of how or when their captivity will end.

The prisoners exist in a legal twilight zone as muddled as the overall Middle East conflict. Eles Dobronsky, a Tel Aviv lawyer and reserve officer who acts as Army spokesman for the prison camp, conceded in an interview that "a very difficult and delicate question" surrounds Israel's right under international law to hold the prisoners, who include 1,000 Lebanese imprisoned in their own country, about 60 foreigners and the rest Palestinians.

Moreover, from the outset of the war in Lebanon, Israel declared that it would not grant prisoner-of-war status under the Geneva Convention to the Palestinian guerrillas it captured because it considers them "terrorists." The Ansar prisoners are classifed under separate Geneva Convention provisions dealing with civilians detained in war.

Yet, Dobronsky volunteered during the interview, two rights that should be granted to civilian detainees are denied to the Ansar prisoners--the right to a canteen where prisoners can purchase certain items (the Ansar prisoners have no money and do no work in the camp) and the right to visits by their families.

The camp's 250 tents are organized into 30 sections, each surrounded by barbed wire. Military police patrol outside the camp while other soldiers in machine-gun-equipped watchtowers ring the area. Across a dirt road that splits the center of the camp, about 1,000 Israeli soldiers live in their own tents.

The prisoners range in age from the mid-teens to their fifties. There is no hot water, but the Israelis say they are making efforts to provide it. The men do their own cooking with the food and cooking gas provided by the Israelis, exercise on their own, sometimes organize sports activities.

And they wait, hoping they will be among those who intermittently are released but never knowing for sure, making Ansar, in Dobronsky's words, a place of "illusion and frustration."

It is also, by all accounts, a much better place than it was in the early weeks of the war when the Israelis chose the isolated spot near the town of Ansar and a small airstrip to contain the unexpectedly large number of Palestinian guerrillas they captured. The airstrip is now a full-fledged runway able to handle heavy Israeli cargo planes.

In the beginning it was clearly overcrowded, containing at one point, according to Dobronsky, almost 9,000 prisoners in fewer tents than today. Living conditions were even more primitive then, because Ansar was established in haste and viewed as a temporary facility.

"Nobody knew then it would take seven months," Dobronsky said.

It was during those summer weeks, when fighting still raged around Beirut, that most of the instances of beatings and other forms of brutality alleged by former prisoners are said to have taken place in Ansar and other Israeli facilities. Israeli officials deny the allegations and promise to investigate any specific incidents brought to their attention. Red Cross officials will say only that beating is not used to punish prisoners in Ansar today.

Five prisoners have died or been killed since Ansar was established, according to the Israelis. One suffered from cancer and died after being taken to a hospital. A Palestinian youth died one August night in his tent and was diagnosed as having succumbed to malnutrition that began before his imprisonment.

In September, when hundreds of relatives of the prisoners gathered near the prison gates, Israeli guards opened fire on prisoners who attempted to climb the camp's fence, wounding eight of them.

The worst incident occurred Dec. 2, when an Israeli soldier manning a machine gun on an armored vehicle accidentally discharged his weapon. Two prisoners were killed at once, a third died in a hospital and three others were wounded.

Israeli authorities say the soldier faces a possible court-martial, and the head of the prisoners' committee said the incident is accepted by the Ansar inmates as an accident.

Much of the credit for improving conditions here is given, by the prisoners and others, to Meyer Rosenfeld, a ruddy-faced, 55-year-old reserve Army colonel whose duties place him in charge of all Israeli military prison facilities.

In a tacit admission that things were not going well at Ansar, Rosenfeld last October took over personal command of the camp, relieving the previous commander. "He did not have the experience, it's not that he's a bad person," Rosenfeld said.

Rosenfeld said he found the camp overcrowded, with a high level of tension between prisoners and guards and winter closing in. He ordered new winter tents, kerosene heaters and a new, more carefully prepared, second area for prisoners.

He also lifted all restrictions on Red Cross access to the camp and allowed prisoners who were members of the same family to be united in the same prison sections.

These improvements came over weeks in negotiations between Rosenfeld and the prisoners' committee. Rosenfeld established the committee, naming the PLO colonel, believed to be the highest ranking officer in Ansar, as its chairman, along with a major from a rival PLO faction, a Palestinian doctor and a Lebanese lawyer.

"One reason it is quiet since I got here is that I talk to them," Rosenfeld said.

Keeping Ansar quiet, reducing the "tension level," is the Israelis' main preoccupation at the camp. They have been warned by outside observers that with so many men in one area that is enclosed only by fences, barbed wire and earth barriers, a major disturbance or escape attempt would undoubtedly lead to gunfire by the guards and risk a bloodbath.

To prevent this, the Israelis acknowledge the use of collaborators inside the camp, where the prewar PLO command structure apparently has survived largely intact. "We have information in order not to be surprised," Dobronsky said.

The Israelis also continue almost nightly meetings with the prisoners' committee, listening and sometimes responding to their complaints. Recently, the prisoners complained that one man had been forced to stand all night while awaiting interrogation. Rosenfeld said he has since taken charge of the tent where prisoners are held before questioning.

This week, the prisoners also staged a peaceful demonstration, complaining of inadequate medical treatment that is provided by 14 doctors who are also prisoners and, when necessary, seven Israeli doctors who are stationed at the camp.

Rosenfeld acknowledged that some prisoners should be released for medical reasons, but said that there is a dispute over the number: "Our doctors say there are about 100 to 130, the Red Cross says 300 to 350 and they the prisoners say 1,240."

But none of these physical improvements has made Ansar a pleasant place, or relieved the anxiety or uncertainty of life in the camp. The Israelis continue to release prisoners after a review by an appeals committee, but according to criteria that are unclear except that the Israelis say they will not release known PLO officers or leaders.

New prisoners also continue to be brought to Ansar, sometimes as many as 20 a week, according to Dobronsky. Interrogation of prisoners, although reduced, continues and is a major complaint .

"There is no torture now in Ansar," the head of the prisoners' committee said. "But many people are missing. We don't know whether they are free or where they went."