After a four-month lull in fighting, the two largest Palestinian (search) terrorist groups are threatening to withdraw from a cease-fire, accusing Israel of violating the truce with continued military operations.

Leaders of Hamas (search ) and Islamic Jihad, which have carried out dozens of suicide bombings in recent years, said they would make a final decision in the coming days. The groups made their announcements late Sunday after a meeting of 13 Palestinian factions in Gaza.

"It looks like Israel will continue in this aggression and we cannot accept that anymore," said Mohammed al-Hindi, an Islamic Jihad leader.

Israeli Prime Minister Ariel Sharon (search) and Palestinian leader Mahmoud Abbas (search) declared the cease-fire at a summit in Egypt in February, hoping to end more than four years of fighting. The following month, the Islamic terrorists agreed to honor the deal.

The ceasefire has brought a sharp drop in violence, although sporadic bloodshed has persisted. Abbas met with terrorists in Gaza last week in an effort to shore up the truce following a new flare-up.

In the meetings, Abbas agreed to give the terrorists a role in preparations for the planned Israeli withdrawal from the Gaza Strip. The Palestinian Authority also released two Islamic Jihad prisoners it had been holding for involvement in a Feb. 25 suicide bombing in Tel Aviv.

Representatives of Hamas and Islamic Jihad agreed to honor the cease-fire, but warned they will strike at Israel if they feel they are attacked. They repeated the warning over the weekend.

Saed Sayem, a Hamas spokesman, said his group's patience was wearing thin. "Israel is committing daily violations," he said after Sunday's meeting. "We are going to reconsider our stance if Israel continues its aggression."

The Israeli army has greatly reduced its activities but continues to arrest or attack terrorists it believes are actively involved in violence against Israelis.

A collapse in the cease-fire would mark a serious setback for Abbas, who is under Israeli pressure to rein in the terrorists. Abbas has refused to confront the terrorist groups, preferring to negotiate with them.

A resumption of violence would also hinder Abbas' efforts to crack down on a growing wave of lawlessness in the Palestinian areas.

The Palestinian Authority on Sunday carried out its first executions since 2002, killing four convicted murderers in a campaign meant to stop the chaos.

Abbas has made public order a top priority, but his forces have been weakened by internal rivalries, a lack of resources and years of fighting with Israel.

Despite Abbas' efforts to revamp his security forces, terrorist groups and armed gangs continue to operate with virtual impunity, often clashing with rival factions or police.

Sunday's executions appeared to be an attempt to deter criminals and send a message to the public without directly confronting the terrorists. None of the executed men was believed to be affiliated with any of the major terrorist groups. Their crimes date to the mid-1990s.

"There is a new policy of enforcing the law, to face and fight the chaos and lawlessness in the Palestinian territories," Interior Ministry spokesman Tawfiq Abu Khoussa said.

The death penalty was established in the territories in 1994. But the late Palestinian leader Yasser Arafat halted it in 2002 after criticism by European countries and international human rights groups.

The Gaza Center for Human Rights, a Palestinian monitoring group, said the men executed Sunday were common criminals serving murder sentences in Palestinian prisons.

Rigi Sorani, chairman of the human rights group, condemned the killings and accused the Palestinian Authority of carrying out a "token" execution that failed to go after the gunmen and rogue elements of the security forces responsible for much of the recent violence.

Including Sunday's killings, the Palestinian Authority has executed 13 people.

Some 47 Palestinians remain on death row, about half of them convicted collaborators with Israel. Palestinian officials said last month they had suspended plans to execute the collaborators, fearing their deaths would inflame tensions with Israel.