Palestinian guerrilla leaders pledged stronger attacks against Israel today after Israeli warplanes bombed and strafed offices and a training center of the Palestine Liberation Organization here and in southern Lebanon.

"We have made a decision to retaliate to any Israeli aggression," Salah Khalaf, also known as Abu Iyad, the number two official in the PLO, said. He said his guerrillas would mount a stronger counterattack than that by Israel today and warned that with every Israeli "violation of the cease-fire we will respond, and we will hit civilian targets in northern Israel."

Later today, in an apparent beginning to a new round of attacks, Palestinian guerrillas in southern Lebanon shelled Israeli settlements across the border in Israel.

The raids by Israel's American-made F16s, in retaliation for the shooting in London last night of Shlomo Argov, Israeli ambassador to Britain, hit PLO sites in Beirut and in southern Lebanon, near the Israeli border.

Lebanese Premier Chafik Wazzan called for an emergency meeting of the U.N. Security Council to discuss the Israeli raid and President Elias Sarkis met with U.S. Ambassador Robert Dillon as the raids were going on late this afternoon. There was no report of the outcome of their talks.

The PLO continued to insist that it had nothing to do with the shooting in London but, because of Israel's policy of swift retaliation following such attacks, the Palestinian guerrillas in Lebanon had been on alert for several hours when the raids began about 3 p.m.

The official state television said tonight that at least 45 people had been killed and 150 wounded. Earlier, Palestinian officials had put the death toll at 32.

The casualty toll included several Syrian soldiers serving with the Arab peace-keeping force in Lebanon. A military spokesman in Damascus said two Syrians were killed in the raids and six injured, but sources at the Beirut Hospital said 12 injured Syrian soldiers were being treated there. One, Abdel Mouteh, said he was manning a roadblock when he was hit.

Most of the casualties appeared to have come from the bombing of Beirut's former municipal sports stadium, called Sport City, which is now a training base of Fatah, the largest faction of the PLO.

An ambulance worker said the upper two floors of the three-story stadium had collapsed onto its foundations. "Families must have been living there. My coworkers are still digging for more bodies," said Mohammed Ashashi. "It was sheer panic. Sometimes we just bumped against each other with our stretchers."

Palestinian sources said that some guerrillas, who were training inside, were also trapped under the rubble.

Ashashi said he saw two jeeps, one truck mounted with antiaircraft guns and three ambulances transformed into charred and twisted metal in the stadium parking lot.

Israeli jets dove in close to the stadium, dropping a trail of bright thermal balloons to deflect the heat-seeking antiaircraft missiles being fired by the guerrillas and soared upward as other planes swooped in lower firing straight on target.

From a distance, flames could be seen billowing out of the stadium, once an impressive sports center built by former president Camille Chamoun in the late 1950s. Radio reports said the fires were made worse by ammunition stored in the lower floors of the stadium.

Alain de Bos, a French cameramen working for CBS, was superficially wounded in his arm, head and foot as he was filming the first two sorties of Israeli planes over the stadium. "Just as rescue teams went in and we were close enough to shoot film , the planes came back and struck. We did not realize what was happening before they came back again," de Bos said.

At the Beirut Hospital near the airport road, which was bombed on both sides, hospital director Abdullah Nawfal said that most of the 43 wounded being treated there were from a Palestinian women's teaching institute opposite the stadium and the nearby Bourj Barajneh Palestinian refugee camp.

Other targets of the Israeli raid were PLO offices in the Farkhani section of southern Beirut, the Shatila and Sabra refugee camps near Beirut and Palestinian positions in southern Lebanon, including Nabatiyeh.

At the Palestinian-run Gaza Hospital in Sabra, Palestinian Red Crescent ambulances were still bringing in wounded from southern Lebanon hours after the raid. Travelers from the area said artillery duels between Palestinian guerrillas and Israelis continued into the night as Israeli gunboats remained close to the Lebanese shoreline and planes dropping flares circled villages.

A Gaza Hospital official, Samia Nasser, said she had admitted 59 wounded, and 14 dead were brought to the hospital morgue.

People waited around the hospital entrance for relatives believed missing or wounded in the raids. Among those waiting was Radwan Mawlawi, the Lebanese Information Ministry's acting general director, whose niece, Ghina Mawlawi, 17, was killed.

Three-year-old Mohammed Mustafa Berri lay in a small bed with his arm and shoulder in bandages. He was playing when the planes came, according to his mother, who said she and her family lived in the stadium.