Israeli occupation forces killed at least 11 Palestinians who were watching firefighters put out a fire in a Gaza refugee camp, just hours after a bus bombing that killed 15 Israelis, witnesses said. More than 100 people were wounded in the attack on the Jabalya refugee camp, which came during a sweep by the Israeli occupation army. The occupation army did not immediately comment.

A gun battle had erupted in Jabalya during an overnight Israeli operation in the refugee camp, witnesses said, and continued as occupation troops pulled out of the area and withdrew into an alley.

Residents came out into the streets to see the aftermath of the raid as the gun battle raged nearby. They watched smoke and flames pour out of a three-story building. Firefighters tried to extinguish the flames, witnesses said.

Suddenly, the occupation troops fired heavy machine guns from tanks and shells, they said, and a helicopter hovered overhead fired missiles. Blood and body parts flew through the air, witnesses said.

Palestinian witnesses being treated in a Gaza hospital gave conflicting reports over whether the tank shells or missiles hit the crowd, however, they agreed that the group hit was unarmed and was watching the firefighters at work.

Marwan Abu Shamales, 49, said he came out of his house after he believed the occupation troops had withdrawn.

"When the fire engines arrived and started working to control the fire the sound of an explosion was heard and I felt like flames were cutting into my leg," Shamales said.

"I started screaming and I fell down. My bad luck was I fell on the two legs of a dead man and it covered my face with blood," he said.

Doctors at the hospital said most of the injuries they treated were caused by tank shell shrapnel.

Earlier, two other Palestinians were killed during the occupation army's operation in Gaza. The occupation army blew up two buildings, including one belonging to a Hamas activist.

A Reuters TV cameraman and photographer were among those wounded in the earlier fighting.

The occupation army sweep came as Israelis mourned the 15 passengers killed by the resistance bomber in Wednesday's bus bombing, which ended a two-month lull in resistance bombings. The blast injured 55 people.

About 10 of the victims were high school students - among them 14-year-old Avigail Leitner, a U.S. citizen, authorities said. Two occupation soldiers were also killed.

Police said the resistance bomber, Mahmoud Hamdan Kawasme, 20, of the West Bank city of Hebron, was carrying a letter praising the Sept. 11 attacks. No group claimed responsibility for the bus blast.

In a first response to the attack, Israel's Security Cabinet ordered the closure of the West Bank and Gaza Strip until further notice, banning all Palestinians from entering Israel, the Israeli occupation army said early Thursday. Later, about 50 Israeli tanks accompanied by helicopter gunships moved deep into the Jabaliya camp.

Israel's new hard-line government had pledged earlier to step up strikes against resistance strongholds in the Gaza area. Dozens of Palestinians have been killed in more than two weeks of raids.

Bus No. 37 was packed with students from Haifa University when it stopped in the hilltop neighborhood of Carmelia at 2:17 p.m. to let off passengers.

"I suddenly heard an explosion," said bus driver Marwan Damouni, an Israeli Arab, who was being treated at a hospital. "I didn't feel anything. I didn't hear anything. I opened my eyes after a minute and saw blood all over my arms."

The explosion blew off the bus roof, shattered all its windows and toppled nearby palm trees. Floodlights cast an eerie glow on the scene, illuminating the charred skeleton of the vehicle.

The bomb was laden with metal shrapnel for greater deadliness, according to Police Commissioner Shlomo Aharonishki. Initial reports said the blast was caused by 130 pounds of explosives.

Ovadia Saar, who was driving another bus just behind the one that was attacked, said he saw "the back of the bus fly into the air, and the windows blew out and a great cloud of dust covered the bus."

"I got out and ran toward the bus. It was a horrible sight. There were a few bodies in the street," he said. "Those we saw breathing, we evacuated."

A spokesman for the Islamic resistance group Hamas, Abdel Aziz Rantisi, praised the bombing but did not claim responsibility. "We will not stop our resistance," he said. "We are not going to give up in the face of the daily killing" of Palestinians.

After the bus bombing, some Palestinians in Gaza called each other on cell phones. Some were jubilant.

"It's about time. They've kept on hitting us and killing us, and now we've struck back," said an ice cream vendor in Gaza, who refused to give his name.

Police did not immediately have details on the American victim, Avigail Leitner, and her links to the United States.

The indefinite closure of West Bank and Gaza threatens to aggravate a crippled Palestinian economy. Two reports issued by the United Nations and World Bank on Wednesday linked such closures to the economic woes, saying almost 2 million Palestinians live on less than 2 dlrs a day.

The Haifa blast was the first terror attack in Israel since Jan. 5, when a pair of resistance bombers killed 23 people in Tel Aviv. It was the first bus bombing since Nov. 21, when 11 passengers were killed in a resistance attack in Jerusalem.

PHOTO CAPTION

A Palestinian man wounded during the Israeli Incursion into the Jabalya refugee camp wait to be treated at the emergency room at the Shifa hospital in Gaza city, Thursday, March 6, 2003. Israeli occupation forces backed by tanks and attack helicopters killed at least 11 Palestinians on Thursday who were watching firefighters put out a fire in the Jabalya refugee camp in Gaza, witnesses and hospital officials said. More than 100 people were wounded. (AP Photo/Karel Prinslo