Palestinian terrorists aboard rafts landed on the northern coast of Israel yesterday, hijacked a tour bus, and went on a shooting rampage that climaxed in a deadly gun battle at a police roadblock just outside Tel Aviv.

At least 30 persons were killed and scores wounded, by official Israeli count, in what appears to be the worst terrorist attack in Israel's history.

A communique issued in Beirut by the largest Palestinian guerrilla organization, Al Fatah, claimed responsibility for the operation, and said it was launched as part of the Palestinians' determination to step up "revolutionary armed violence against Zionist occupation."

The communique said the attack was code-named "The Operation of the Martyr Kamal Adman," after a Palestinian leader killed in an Israeli commando raid on the center of Beirut in April 1973.

Prime Minister Menachem Begin immediately postponed his trip to the United States and there was speculation on the possibility of an Israeli counter raid on Palestinian camps in Lebanon.

By the time the main incident ended at a roadblock just north of Tel Aviv, the tourist bus was a smoking skeleton and hundreds of Israeli army and police forces were scouring beaches and farms in the area for members of the terrorist gang who apparently escaped during the gunbattle.

Israeli censors put heavy restrictions on reports of the fighting and numbers of casualties, but the following account was pieced together from official and eyewitness reports:

Israeli radio said an unspecified number of guerrillas came in on rubber dinghies and landed on the coast near a kibbutz named Maagan Michael, about 15 miles south of Haifa, late in the afternoon.

They then moved onto the coastal highway, stopping two buses full of Sabbath tourists, they forced all of them - including about 30 children - into one of the buses, and headed down the highway toward Tel Aviv, shooting over the heads of cowering passengers at passing cars.

There were no reports of foreigners among the victims on the bus.

Israeli soldiers and police rushed to the coastal highway, closing it off to further traffic and setting up a roadblock near a country club seven miles north of Tel Aviv. U.S. Ambassador Samuel Lewis lives in the posh suburban coastal area of Herzliya Petuach not far from the club.

As the bus approached the roadblock, police marksmen shot out the tires and a gunbattle broke out. Some of the guerrillas left the bus with the passengers, reportedly numbering 71, crushed into the back of the vehicle. The bus then erupted in flames. Some reports said the attackers had set off a bomb or wired the bus to explode. Dozens of civilians were wounded and taken to hospitals in and around Tel Aviv and calls went out for emergency blood donations. There were no reports on the number of Israeli military casualties or of casualties among the attackers.

Moshe Krieger, one of the survivors, gave the following account of the start of the incident to Israeli radio:

"We returned from a trip to a stalagmite cave. When we got to the 63-kilometer sector of the coastal road, about 4:40, we saw ahead of us a group of armed people getting on the road heading toward the bus with their weapons at the ready.

"At the first minute, we thought - the people in the front part of the bus - it was a hoax. But before we figured out was happening, they ipened up on us with bursts of fire. The first bursts hit people in the front end of the bus."

A youth who passed by the scene just after the first bus was attacked said, "We saw wreckage and a lot of blood. At first we thought it was a road accident and we wanted to help. Then we heard policeman shouting "Terrorists! Terrorists! A car went by full of bloodied people. I don't know if they were dead or alive."

A passenger on the second bus, Avrehim Shamir, said it stopped when "we saw the (first) bus with a wounded driver." Then, he said, "a Mercedes-Benz f ull of terrorists came by and ordered us all into one bus."

Another passenger said that there were "six or seven" terrorists and they continually fired over the heads of passengers as they drove down the highway toward Tel Aviv.

AShamir said that the bus came under "heavy fire" as it approached the roadblock just north of Tel Aviv.

"The terrorists were huddling on the floor with the paseengers," he said. "Suddenly I got a gun away from one terrorist and I think I shot two of them. One of them shot me."

Another passenger said that police broke windows of the bus and started yelling at the passengers to jump out.

policeman at the scenes said the gunbattle lasted for about 20 minutes when the bus exploded in flames.

Reports from eyewitness broadcast on Isarel radio said that the Palestinians sang patriotic songs, cursed both Eygptian President Anwar Sadat and Prime Minister Begin and killed several passengers who begged fro their lives.

When the battle at the Tel Aviv roadblock came to an end, the gutted smoking bus stood at the police barriecade about half a mile from the shore as police sealed off the area and an intensive hunt began for some of the guerrillas who were believed to have escaped. Motorists stopped along the coastal highway were urged to shine the lights of their cars into the roadside scrub and helicopters with powerful searchlighrs hovered overhead.

Civilans reservits armed with rifles and sub-machine guns set up roadblocks and ordered all residents in the area to remain indoors.

A Reuter reporter. Arik Bachar, in one of the first reports from the scene of firelight said the attack brought battlefield scenes to the very heart of the Jewish state.

His report said that flares lit up an eerie scene at the near by country club, which would have been crowded on a normal Saturday night. Last night, the flames revealed empty tennis courts. Guests staying at the club, mostly foreign tourists, were ordered to air raid shelters.

Special squads of the Jewish rabbitnate - the only personnel authorized to handle corpses in Isarel - were trying to sort out the remnants of at least seven dead on the bus.

One df the dead was a girl who appeated to be about five years old. She held a toothbrush in her hand.

A few hours after the bus explosion, a wounded guerrilla was discovered only yards from the wrecked vehicle. The police rushed him away.

Police sappers removed several live hand grenades thrown by the guerillas when they rushed off the bus.

The guerilla operation was mounted almost exactly in which eight Palestinian raiders took over a hotel on the Tel Aviv waterfront. In the fighting that followed. 11 Israelis and all but one of the attackers were killed