The U.N. Security Council voted yesterday to send another 2,000 peace-keeping troops to southern Lebanon following a Tuesday night battle that left three U.N. troops dead and nine wounded.

The 15-member Security Council voted 12-0 to send the additional 2,000 men - one contingent each from Iran, Fiji and Ireland - into the troubled region to join the 4,000 man force it approved earlier.

The Soviet Union and Czechoslovakia abstained in the vote and China refused to participate.

Meanwhile, Lebanese leftist guerrillas were blamed for Tuesday night's attack on U.N. troops near the southern Lebanon port of Tyre that left two French soldiers and one Senegalese dead and nine Frenchmen wounded.

Palestinian military leaders denied initial reports that Palestinian guerrillas were involved in the fighting, which broke out as local cease-fire talks were getting under way.

A Lebanese leftist group, which lost two men killed in an earlier clash with French troops, later said in a communique that the fighting around Tyre had begun when a U.N. patrol opened fire on one of its guerrilla groups that was heading toward Israelis lines.

The communique was issued by the Popular Resistance Front for the Liberation of the South from Occupation and Fascism. It said its men returned the fire, and the fighting then escalated.

In Paris, Washington Post correspondent Ronald Koven reported that the French government appeared inclined to accept the Palestinian claims at face value.

Whoever it was that shot at the French, Israeli officials feel that the recent attacks on U.N . troops in Lebanon demonstrate the mistake in pressuring Israel to withdraw hastily from southern Lebanon before the U.S. peacekeeping force is fully deployed, Washington Post correspondent H.D.S. Greenway cabled from Jersalem.

An Israeli Foreign Office spokesman yesterday described the situation in the south of Lebanon as "difficult and complicated."

While Tuesday's fighting took place outside the area that Israeli forces occupied during their invasion of southern Lebanon five weeks ago, officials said Israeli forces would be reluctant to accelerate their withdrawal from the 6-mile deep strip of Lebanon they still hold if the French troops continue to have difficulty controlling armed activity in the Tyre area.

U.N. Secretary General Kurt Waldheim told the Security Council yesterday that he was pursuing his efforts to "secure a timetable" for a complete Israeli withdrawal.

Waldheim said Palestine Liberation Organization chief Yasser Arafat had "assured me of his cooperation" in preventing more killings of U.N. troops.

Meanwhile, Capt. Jean Menegaux, a French officer with the U.N. force, gave a detailed account of Tuesday's fighting, which he described as "a real battle with heavy weapons."

He said the French commander, Col. Jean-Germain Salvan, who was wounded in the fighting, had met with PLO leaders at 6 p.m. local time to discuss earlier clashes in which French soldiers had killed Lebanese leftist gunmen.

Ten minutes later, a U.N. truck carrying food supplies in the area was destroyed by a rocket-propelled grenade and an accompanying jeep was hit by automatic weapons fire, he said.

The colonel immediately broke off the peace talks and led a strong force into the countryside to investigate the incident.

Capt. Menegaux said the U.N. troops came under heavy fire, reinforcements went out and fighting spread quickly.

"They were hitting us from several buildings as well as from camouflaged positions in the orange groves," he said. "In the first few minutes, I saw one of our armored cars exploding in flames after being hit by a rocket."

At the same time, a French soldier was killed when the barracks was hit by rocket and mortar fire, he said.

After almost two hours, PLO officials appealed for a cease-fire and Col. Salvan agreed to drive with them to the front line to implement it.

Capt. Menegaux said the colonel was standing in the back of a PLO truck with a Palestinian liaison officer when it was ambushed about 400 yards from the barracks. The three occupants of the truck were wounded.

Meanwhile, the United Nations Relief and Works Agency for Palestine refugees (UNRWA) announced yesterday that it has decided to move its headquarters from Lebanon for reasons of "efficiency and safety of personnel," according to Agence France-Presse.

The headquarters could be transferred to Damascus, Amman or Vienna, the agency said. UNRWA, established by the U.N. General Assembly in December 1949, stressed that the transfer of its headquarters from Beirut would not affect its services to 201,000 refugees registered with it in Lebanon. They represent less than 12 percent of the Palestinian refugees registered with the agency throughout the Middle East, it said.