GAZA CITY, Gaza Strip - Hamas security arrested dozens of supporters of the rival Fatah group, hurled grenades at the home of a Fatah leader and set up checkpoints across Gaza on Saturday after a mysterious beachside blast that killed five Hamas members and a 6-year-old girl.
Hamas leaders blamed Fatah for Friday's explosion, and began the toughest crackdown against the rival group in recent months. A Gaza-based human rights group reported Hamas security officials arrested at least 160 Fatah loyalists, and some 40 institutions connected to the group were raided.
Fatah leaders denied involvement, and an aide to Palestinian President Mahmoud Abbas said the crackdown is reducing prospects for eventual reconciliation.
If Hamas was targeted, it would be the deadliest such attack since the Islamic militants ousted Fatah-allied security forces from Gaza in a violent takeover more than a year ago.
The blast went off underneath a car parked near a crowded Gaza City beach on Friday evening, Hamas officials said. At the time, a group of Hamas activists was picnicking on the beach, Hamas said. The blast shattered the windows of the white sedan and damaged its doors.
Three Hamas members and the girl were killed immediately. Two more Hamas activists died of injuries Saturday and 15 people were wounded, according to a statement by the Palestinian Health Ministry.
Hamas Prime Minister Ismail Haniyeh convened an emergency government meeting Saturday. In a statement released after the meeting, the government said it had instructed authorities "to find the people who were involved in the horrible crime yesterday."
If convicted, the perpetrators could face the death penalty.
Among the dead were a senior Hamas field commander and Iyad al-Hayeh, a nephew of Hamas lawmaker Khalil al-Hayeh, health officials said. Osama al-Hayeh, a son of the lawmaker, was wounded.
Tensions were palpable on Gaza's streets following the blast.
Thousands of Hamas loyalists marched in the funeral of the explosion's victims, waving their movement's green flag. Gunmen fired automatic rifles into the air and angrily vowed revenge.
"The collaborators who did this must be hung in Palestine Square and shot," al-Hayeh, the lawmaker, said in a eulogy, referring to Gaza City's main square.
"The people who stand behind this (attack) are from Fatah," al-Hayeh said. "We hold their leaders responsible ... and say, either be nationalists or collaborators, the choice is yours."
Al-Hayeh had previously survived two Israeli assassination attempts that killed members of his extended family.
Hamas policemen set up checkpoints on major thoroughfares and roads leading to security compounds, checking suspicious cars and forcing others to slow down.
Dozens of Fatah supporters were rounded up, said Ibrahim Abu Naja, a prominent Fatah leader in Gaza. Abu Naja said Hamas police also raided offices and institutions belonging to Fatah overnight. Abu Naja's own office was raided on Saturday.
The offices of independent lawmaker Ziad Abu Amr and of Zakariya al-Agha, a member of the PLO Executive Committee, were among those targeted. Another senior Fatah leader, Abdel Rahman Hamad, fled his home amid concerns he would be arrested, his family said.
In one attempted arrest, Hamas police fired four rocket-propelled grenades at the home of a local Fatah leader and briefly exchanged fire with his guards, witnesses said. Police then searched the house, but didn't find the wanted man, Mohammed Aweidat.
The Palestinian Center for Human Rights in Gaza reported that some 160 Fatah loyalists and members were rounded up. The center suggested the number could be higher. Another 40 institutions loyal to Fatah were raided, including charities, a center for the disabled and a folkloric center.
An unknown offshoot of the Fatah movement, calling itself the "Awda Brigades" claimed responsibility for the attack in a statement to reporters. But the claim could not be verified independently.
In the West Bank, Abbas aide Ahmed Abdel Rahman condemned the explosion and said the Hamas crackdown is "irresponsible."
"These measures empower separation (of Hamas-ruled Gaza and the Fatah-run West Bank) and reduce chances of a national dialogue and of restoring unity of the two parts of the country," he said.
Friday's beachside explosion was the third of the day.
The first went off outside the Al Jazera cafe, killing the assailant and wounding three people. The cafe had been hit twice before this year, presumably by hardline Muslims who target record shops and other businesses seen as symbols of Western influence.
Later, a bomb exploded outside the house of a Hamas lawmaker, Marwan Abu Ras, causing some damage, but no injuries. A Fatah activist was arrested as a suspect.
During the past year of Hamas rule, several bombs have struck Hamas targets in what the Islamic militants believe are attempts by Fatah to try to destabilize the situation in Gaza. Assailants have also attacked music shops and Internet cafes, presumably targeting them as signs of Western encroachment.
