A Palestinian detonated a powerful truck bomb at the main pedestrian crossing between Israel and the Gaza Strip on Thursday, causing extensive damage that dealt a serious blow to Gazans' hopes of opening up their sealed-off territory.

Although the bomber killed only himself, the magnitude of the explosion _ which shook buildings for miles _ raised fears that Palestinians are adopting tactics used by al-Qaida, Hezbollah and other extremist groups.

The attack at the Erez crossing also reinforced skepticism about Egyptian-led efforts to bring a truce to the violence-wracked area and hurt international efforts to ease the Israeli-led blockade of Gaza, imposed after Hamas militants seized control of the coastal territory almost a year ago.

Later, at the Karni cargo crossing some 5 miles away, a protest against the blockade turned violent, with Palestinians accusing Israeli troops of firing into the crowd of thousands, killing a 22-year-old man and wounding 16 other people.

In chaotic scenes, swarms of people darted along a narrow road near the crossing, fleeing tear gas and live bullets as Israeli tanks rumbled into Gaza from Israel. The military said soldiers opened fire after spotting armed men in the crowd, including one carrying an anti-tank missile, and that the gunmen returned fire.

"Zionists, death is coming," loudspeakers blared. "You will fall, your corrupt state will fall," the crowd chanted _ reflecting the intensity of Gazans' bottled up frustration a year into Hamas' turbulent rule, a period in which 80 percent of Gaza's adult population has descended into poverty, according to the United Nations.

Two little boys ran into a field flanked by tanks while adults in the crowd loudly admonished them to come back. Protesters climbed electricity poles to hoist the Hamas flag. Ambulances rushed in to evacuate the wounded, and plumes of black smoke climbed into the sky after protesters set tires afire.

The violence at Gaza's border crossings came as Egyptian mediation efforts to forge an Israeli-Hamas cease-fire ran into trouble, with several Hamas leaders claiming the truce talks had failed. The leaders, who spoke on the condition of anonymity because the group had not made an official statement, blamed the breakdown on Israel's failure to accept a six-month truce.

However, Israeli military officials, who also spoke on the condition of anonymity citing the lack of a formal announcement, confirmed that Amos Gilad, a senior Israeli defense official, will travel to Egypt on Sunday for more talks _ a sign the truce remains on the table.

Khalil al-Haya, a Hamas leader participating in the talks, said negotiations were still going on and Palestinian militant groups planned to meet to discuss the status of the talks.

Abu Ahmad, a spokesman for Islamic Jihad, one of two groups claiming joint responsibility for the bombing at the Erez crossing, said the attack was meant to "send a message" to Israel that if it didn't accept a truce, "Gaza is not going to be a place where you will enjoy stability."

The attack at the Erez crossing comes in the wake of two audio tapes from Osama bin Laden in which the al-Qaida leader portrayed himself as the only true defender of the Palestinians.

Hamas has tried to distance itself from bin Laden's remarks _ aware that too close an association is not likely to help the Palestinian cause and that global jihadists have a stake in undermining any cease-fire deal with Israel.

Truck bombs are not commonly used by Islamic Jihad and the other group participating in Thursday's attack, the Al Aqsa Martyrs' Brigades. Extremist groups linked to al-Qaida have often used them.

Boaz Ganor, a leading terrorism expert in Israel, said Thursday's attack shows the "infiltration" of the Lebanese guerrilla group Hezbollah and their Iranian sponsors into the Gaza Strip. Continued...