Israeli warplanes bombed targets in the downtown section of the city today in their deepest penetration of West Beirut and demolished an apartment block in the residential area amid sharply escalated fighting between Palestinian guerrillas and Israeli forces ringing the capital.

The Israeli raids sparked a rocket attack by the Palestinians on Israeli lines and Christian enclaves in East Beirut and the port of Juniyah 11 miles north of Beirut.

According to the Lebanese newspaper An Nahar, some of the rockets fired at Juniyah hit a Red Cross ship from Bremen, West Germany. The ship had arrived from Larnaca, Cyprus, to unload relief supplies. One crewman was reported killed and several injured.

Palestinian spokesmen reported more than 100 people were killed and at least 200 wounded in bombing and shelling in and around the city today, but there was no independent confirmation of these figures. It was evident from eyewitness reports, however, that many died when an Israeli bomb hit an eight-story apartment building in West Beirut's seafront Rawshah district, causing most of the structure to collapse.

Many of the inhabitants of the building were reported to be Palestinian refugees and Lebanese squatters made homeless by the 7-week-old war.

Meanwhile, U.S. special envoy Philip C. Habib met in Jerusalem with Prime Minister Menachem Begin and other top Israeli officials amid signs Israel is close to giving up on the use of diplomatic means alone to get Palestinian guerrillas out of West Beirut. Details on Page A16.

The Israeli raids into the luxurious residential section of the city came after five days of air attacks on the southern suburbs, the site of PLO positions and refugee camps. The Palestinian guerrillas and their allies replied with artillery and barrages of Soviet-supplied Katyusha rockets generally aimed at Israeli lines in the hills south and east of Beirut. The radio of the rightist Christian Phalangist militia said several rockets landed in East Beirut and Juniyah, causing several casualties.

Well after nightfall, barrages of Katyushas, fired from mobile launchers moving in and out of populated residential areas of West Beirut, could still be seen streaking across the sky toward Israeli positions.

According to An Nahar, three persons were killed and at least 30 were wounded in the rocket attack on Juniyah.

A Lebanese Cabinet minister said the afternoon air strike, which followed overnight artillery exchanges and shelling from Israeli gunboats off the coast, forced Prime Minister Shafiq Wazzan and his family to take shelter in the basement of their apartment building.

About two hours later, Israeli fighter-bombers returned and struck targets on the southern outskirts of West Beirut, where 5,000 to 6,000 Palestinian guerrillas are trapped with an assortment of Lebanese Moslem militiamen and remnants of a Syrian brigade.

In their second bombing run of the day, the silver planes veered and twisted as flak exploded in the air, and at least one Soviet-made SA7 ground-to-air missile missed its target.

In the second raid, a bomb landed by the Beirut racetrack near the French ambassador's residence. This led to the closure of the main crossing point between besieged Moslem West Beirut and the relatively unscathed Christian eastern sector.

Israel said the second wave of air strikes came after two Israeli soldiers were wounded by PLO guerrillas firing rocket-propelled grenades and light weapons from positions south of the city. An Israeli military spokesman was quoted by news agencies as saying targets of the aircraft were the airport area and the southern outskirts, the sites of Palestinian camps and PLO offices.

There was no immediate explanation for the bombing of the Rawshah apartment building. Residents said there may have been gun emplacements on the beach several blocks away, but no such position was known to exist in or by that building.

After the bombing, mattresses, clothes, furniture and other household items could be seen amid the rubble and collapsed concrete slabs of the building's upper floors.

Next door, the top floors of a 10-story apartment building were blackened and smoldering from a fire caused by the blast.

Down in the street, rescue teams with a bulldozer labored to clear rubble and search for bodies buried under the debris.

For blocks along the Rue de l'Australie, shops, offices and apartments had been damaged by the bomb. Broken glass, downed telephone lines and chunks of concrete littered the streets lined by damaged cars. Residents hastily gathered up their belongings to move deeper into the heart of West Beirut. In one small grocery shop, a merchant with bandages on his face and arms busied himself taking stocks off his shelves for the imminent move.

Speaking angrily about the intensified Israeli air strikes, Lebanese Tourism Minister Marwan Hammade said the subject would be put before an Arab League ministerial committee meeting in Saudi Arabia Wednesday to discuss the results of lobbying in Europe and the United States for a solution to the conflict.

[Habib's negotiations to end the crisis hinge on finding a new refuge for the Palestine Liberation Organization. The PLO response was unclear to a Sudanese offer to accept the guerrillas, but Mahmoud Labadi, a PLO spokesman, appeared to reject the move, The Associated Press reported. "Why should I go to Sudan? I am not a Sudanese," Labadi said. "We are willing to leave Lebanon immediately. Lebanon is not our country. But our homeland is occupied by the Israelis."]

PLO Chairman Yasser Arafat sent messages to leaders of the Soviet Union, Cuba, France, and Saudi Arabia appealing for pressure on Israel to stop its assault on West Beirut.