JERUSALEM, Oct. 1 (AP)--Palestinian gunmen, cheered by rock-throwing rioters, fired on Israeli troops from rooftops and abandoned buildings in clashes across the West Bank and Gaza Strip on Sunday. Seven Palestinians were killed when Israelis returned fire, for a total of 27 in three days of bloodshed over a bitterly contested Jerusalem shrine. An Israeli border policeman was critically wounded, trapped for hours in a tiny Israeli enclave in the West Bank town of Nablus, as Palestinian fire blocked rescue teams from reaching the area. The latest fighting came as Israeli and Palestinian peace negotiators traded harsh accusations instead of new ideas on how to solve their disputes. In an ominous sign of escalation across the West Bank and Gaza Strip, Israeli troops fired anti-tank missiles, hurled grenades, and shot from helicopter gunships. Several Israeli tanks rumbled toward the Palestinian-run towns of Nablus and Ramallah in a warning gesture but did not cross the lines of jurisdiction. The deadliest battle was waged in Nablus over Joseph's Tomb, a tiny Israeli-controlled enclave smaller than a city block and ringed by a cement block wall and barbed wire. An Israeli soldier shot from a lookout post, with only the top of his helmet and his weapon visible. Palestinian gunmen, some in black ski masks, raced up to the wall and fired into the compound where some Jews believe the biblical patriarch Joseph is buried. At one point, two helicopter gunships swooped down and unleashed a barrage of fire, sending hundreds of Palestinians fleeing for cover. The army said the helicopters were brought in to rescue the wounded Israeli officer, who was taken to safety sometime after nightfall. "This is a holy struggle," said Mahmoud Jamal, one of the Palestinian demonstrators who was injured in the face as he and others tried to break down the gate of Joseph's Tomb, which was retained by Israel after it withdrew its troops from the city and other Palestinian towns in 1995. Four Palestinians were killed in the fight, including a 12-year-old boy. In the Gaza Strip, Israeli troops shot and killed three more Palestinians. The chief Israeli negotiator, acting Foreign Minister Shlomo Ben-Ami, said the Palestinian Authority is orchestrating the violence to exert pressure on Israel and extract concessions in the negotiations. His Palestinian counterpart, Ahmed Qureia, said Israel was intensifying the violence and was "committing crimes against our defenseless people." U.S. diplomats were working frantically with both sides to try to rescue the negotiations, but with time already running short--Israeli Prime Minister Ehud Barak faces an opposition threat to topple him in October--prospects looked grim. "We are urging both sides to exercise maximum restraint and put an end to the violence," said P.J. Crowley, spokesman for the U.S. National Security Council. The clashes were triggered by a visit last week by the leader of Israel's hawkish opposition, Ariel Sharon, to a contested Jerusalem shrine, known to Jews as the Temple Mount and to Muslims as Al Haram Ash-Sharif, or Noble Sanctuary.The disputed hilltop was once the home of the biblical Jewish Temple, the most sacred shrine of Judaism. It now houses two major mosques that mark the spot where tradition says the Prophet Muhammad ascended to heaven. The walled compound is the third holiest site of Islam. Palestinians said Sharon's visit was a provocation because it was intended to show Israeli sovereignty. The dispute over who will control the compound is the main obstacle to a peace agreement. Sharon on Sunday denied he was responsible for the violence. "The riots are part of Arafat's policy of applying pressure on Israel and the Americans when he doesn't get what he wants," Sharon said, referring to the Palestinian leader. In three days of widespread clashes, 27 Palestinians have been killed by Israeli fire--six on Friday at the Jerusalem shrine, 14 across the West Bank and Gaza on Saturday, and seven in gun battles Sunday. There was scattered rock-throwing in Jerusalem on Sunday, and an Israeli policeman was injured when a Palestinian drove his car into a group of officers standing by the side of a road. Clashes also spread to Arab towns across Israel, with thousands of residents hurling stones at Israeli police to join what has been described by some Palestinian officials as an escalating religious war. Most Israeli Arabs are Muslims, and the Islamic Movement in Israel has taken a lead role in renovating underground areas of the Jerusalem mosque compound, despite harsh protests by the Israeli government. In addition to Nablus, firefights also erupted in the West Bank town of Ramallah, in the town of Khan Yunis near the Egyptian border and at an Israeli army post close to the isolated Jewish settlement of Netzarim in Gaza. On the outskirts of Ramallah, Israeli troops commandeered a luxury hotel, with Israeli snipers firing from the rooftop and the ground floor dining hall at Palestinian gunmen taking cover in abandoned buildings and behind cars. Dozens of guests and journalists were trapped in the lobby of the New City Inn as the steady staccato of gunfire was heard outside. Near Netzarim, scores of gunmen, cheered on by hundreds of Palestinian rock-throwers, took aim at a fortress-like Israeli outpost. One bearded gunman knelt behind a low wall as he fired his M-16 assault rifle. One demonstrator pleaded with a more hesitant shooter to hand over the weapon so he could have a go. A Palestinian man critically wounded in the exchange lay motionless on the street outside the Israeli post for several minutes before demonstrators made a dash in a lull to drag him away. The victim's white shirt was bloodied in the back, and his head lolled back and forth.

The gun battles were reminiscent of firefights in September 1996, which also erupted because of a perceived Israeli infringement on the Jerusalem mosque compound. At the time, Israel had opened an archaeological tunnel along the shrine. Four years ago, 59 Palestinians, 16 Israelis, and three Egyptians were killed.