Nearly simultaneous explosions tore through two buses in the heart of this southern Israeli city Tuesday afternoon, killing at least 16 passengers along with the two Palestinian suicide bombers and wounding dozens of people in blasts that shattered a five-month respite from major attacks inside Israel.

Israeli police said two Palestinian suicide bombers detonated their explosives within 20 seconds of each other on two buses about 100 yards apart near city hall, shredding bodies and spewing clothes, groceries and schoolbooks through the shattered windows.

"There were burned bodies on the windows and at the entrances of the bus," said Gershon Kalimi, chief of the fire brigades who said he reached the first bus to explode five minutes after the blast. "Then we went to the other bus and we saw the same horrible images: burned bodies, burning bus, trapped people, people lying on the ground, people calling for help."

Beersheba, a Negev desert city 55 miles south of Tel Aviv, had not been hit by suicide bombers during the four years of the current Israeli-Palestinian conflict. But officials said militants had been drawn southward because Israel's construction of a massive barrier and relentless military operations in the northern West Bank have blocked attacks there.

"They went into the soft belly of Israel where the fence has not been erected," said Gideon Meir, a senior Israeli Foreign Ministry official. "The ultimate truth for the necessity of the fence was given today: Wherever there's no fence, it's easy to penetrate into Israel."

The Islamic Resistance Movement, known as Hamas, claimed responsibility for the attacks in announcements from mosques in the West Bank town of Hebron and the Gaza Strip, saying they were retribution for Israel's assassinations of top Hamas leaders in Gaza last spring and the poor treatment of Palestinians in Israeli jails, hundreds of whom are in the second week of a hunger strike.

Palestinian sources identified the bombers as Ahmed Kawasma and Nassim Jabri, who were neighbors in Hebron, about 28 miles northeast of Beersheba. On Tuesday night, Israeli military forces surrounded the houses of both men and ordered their families to evacuate, according to footage aired by the al-Jazeera television network. The Israeli military usually destroys the homes of bombers soon after an attack.

"We went into Hebron this evening following intelligence that the suicide bombers who carried out the attacks today came from a terror network in Hebron," said Maj. Sharon Feingold, a spokeswoman for the Israeli army. She said military forces were expected to increase operations in Hebron in the coming days.

"The fight against terror will continue with full strength," Prime Minister Ariel Sharon said as he prepared to meet with senior security officials Tuesday night to plan a response to the bombings. Sharon said he would also push forward with his plan to withdraw Israeli settlers from the Gaza Strip, a proposal that has been opposed vociferously by hawkish members of his Likud Party.

Palestinian Prime Minister Ahmed Qureia, who was in Egypt on Tuesday, told the Reuters news agency, "Killing civilians, whether from the Palestinian side or from the Israeli side, will achieve nothing except hatred and more enmity, and therefore we condemn that strongly."

The most recent Palestinian suicide attack was on March 14 in the southern port city of Ashdod, where two bombers from the Gaza Strip killed 10 people. Since then, the lull in violence in hard-hit Jerusalem and other cities had brought an unusually placid summer and rejuvenated nightlife that had disappeared in the early months of the Palestinian uprising, which began in September 2000.

Beersheba, a city of 183,000 people, serves as a commercial and service hub for the southern Negev desert region of Israel. There had been one previous attack here, in February 2002, when two Hamas militants killed a pair of Israeli soldiers in a drive-by shooting at the entrance of a military base.

At about 2:45 p.m. Tuesday, the No. 12 and No. 6 Metro Dan buses pulled out of this sprawling city's main bus station. Each made two stops as they headed north, according to Dudi Cohen, chief of police for Israel's southern district. He said police had not determined whether the bombers boarded the buses at the main terminal or at one of the stops.

The No. 12 drove through a main intersection, with the No. 6 about half a block behind, police said. At 2:55 p.m., a blast tore through the No. 12 bus.

"I saw the first explosion and I didn't imagine that it would also happen to my bus," said Yakov Cohen, 43, the No. 6 driver, who said he slammed on his brakes to distance his bus from the explosion ahead and opened the bus's doors to allow his passengers to flee. "The explosion on my bus was 20 seconds later."

Nissin Vakanin, 65, a barber on his way home from work, was standing near the center of the No. 6 bus when the blast roared through the chassis. Minutes earlier he had given up his front-row seat to a middle-aged woman. As he lurched through the charred and smoldering interior of the bus, he glanced at the seat he had given up.

"I saw her dead," said Vakanin, whose peach-colored shirt was splattered with blood and bits of flesh. "I saw the body of the guy next to her and it was all ripped up. Then I realized he was the suicide bomber.

"My conscience is not quiet," continued Vakanin, who was lightly wounded. "I feel guilty that she died and not me."

An hour after the explosion, a head lay in the aisle of the bus about four feet behind the driver's seat. The torso of a victim slumped on the floor nearby. Body parts were scattered across the blackened interior. Fruits and vegetables and diapers from passengers' shopping trips were flung across the bus and out the windows. A pink sandal lay on the top of the step inside the bus.

Ninety-seven survivors were admitted to the Soroka Medical Center, about half a mile from the site of the explosions, according to the center's deputy director, Arnon Wiznitzer. About two dozen people were in serious condition with burns and internal injuries, he said. Dozens more were lightly wounded and at least 15 were suffering psychological trauma.

The construction of the barrier complex of fences and walls, which encompasses sections of the West Bank, has been the focus of criticism by European governments and human rights organizations that say its path is based more on politics than security. Israel's Supreme Court recently ruled that some segments of the barrier impose undue hardship on Palestinians and should be rerouted.

But Israeli officials say the expanding fence line and military operations have brought about the decline in suicide bombings inside Israel. Nine bombing missions have been carried out so far this year, killing 50 people, compared with 23 suicide operations that killed 139 people last year. At the height of the conflict, in 2002, 228 people died in suicide bombings.

Researchers Samuel Sockol and Hillary Claussen in Jerusalem contributed to this report.

People wounded in the bombings in Beersheba are evacuated from the scene. The militant group Hamas claimed responsibility for the attacks.Emergency workers collect body parts from one of the bomb sites in Beersheba, 55 miles south of Tel Aviv.A woman wounded in the attacks is helped as smoke billows in the background after the blasts. Officials said militants had been drawn south in part because Israel's massive barrier to the north has blocked attacks there.