Palestinian gunmen fired more than 30 mortar rounds at Jewish settlements in the Gaza Strip. There were no casualties, reports CBS News Correspondent Robert Berger, but the Islamic militant group Hamas said the attack was retaliation for Israel's killing of a suspected infiltrator near a Jewish settlement.
In response, Israel cancelled a round of security talks with Palestinian negotiators, saying the Palestinian Authority is not doing enough to rein in militant groups.
However, Palestinian and Israeli officers did meet after nightfall Thursday at a Gaza crossing point to discuss cooperation.
"Everything is conditioned on the question, will the Palestinian leader be able to rein in his terrorist groups. This is by no means certain now," said Israeli spokesman Avi Pazner.
Abbas had ordered security forces to stop militants from firing mortars and rockets at Jewish settlements in Gaza.
Palestinian Cabinet Secretary Hassan Abu Libdeh said Abbas took "punitive measures against officers who did not undertake their responsibilities, which led to the latest developments in Gaza."
An official speaking on condition of anonymity said Abbas dismissed Brig. Gen. Abdel Razek Majaidie, chief of public security, police chief Saeb al-Ajed and three other senior commanders. Also, several lower-ranking officers lost their jobs, the official said.
"These are very dangerous developments, and they violate the legitimacy of the Palestinian Authority," Abu Libdeh said. "No one can continue with these violations."
Last month, Abbas ordered that more than 1,000 veteran officers be retired.
Meanwhile, Palestinian Authority security officials reportedly are worried that Hezbollah and Iran are plotting to kill Abbas to thwart the peace process, and that Hezbollah is urging Fatah and Hamas activists to renew their violence against Israelis in the West Bank adn Gaza Strip.
"Hezbollah and Iran are not happy with Abbas' efforts to achieve a cease-fire with Israel and resume negotiations with Israel," a top PA security official told The Jerusalem Post. "That's why we don't rule out the possibility that they might try to kill him if he continues with his policy."
Abbas dispatched an envoy to Lebanon this week to urge Hezbollah to halt attacks.
Palestinian security officials, speaking on condition of anonymity, said the mortars were fired from an area off limits to them. They added that it is very hard to prevent such attacks because they can be launched quickly. However, there was no indication that troops were pursuing the attackers.
Elsewhere, Israeli Prime Minister Ariel Sharon signaled in a newspaper interview Thursday he is ready to release large numbers of Palestinian prisoners involved in deadly attacks — a significant Israeli concession — if militants halt attacks during Israel's planned withdrawal from the Gaza Strip this summer.
Sharon said Abbas stressed during their meeting earlier this week that the release of long-serving prisoners is a top priority.
"He (Abbas) told me simply that it is a major problem," Sharon told the Haaretz daily. In the past, Israel refused to release those involved in deadly attacks, though in recent days it has said it was willing to consider a few isolated cases.
The newspaper quoted Sharon as saying he told Abbas that if the Gaza withdrawal proceeds smoothly he would release larger numbers of Palestinians involved in attacks. Israel is concerned that militants will fire on Israeli troops and Jewish settlers during the withdrawal to portray it as a retreat under fire.
Abbas has secured promises from the armed groups that they will observe a truce, and the Israeli and Palestinian leaders declared an end to hostilities at their summit.
The leaders of Hamas and Islamic Jihad, Khaled Mashaal and Ramadan Shalah, have privately given their word to Egyptian mediators that a truce would be observed, Palestinian officials say, though in public, representatives of the militant groups have distanced themselves from Abbas' truce declaration.
Local gunmen have said they would respond with violence to any perceived Israeli violations.
Abbas and Sharon are to meet again by Tuesday, at Sharon's ranch in southern Israel.
In another development Thursday, Israel opened a main crossing point with the Gaza Strip Thursday, allowing Palestinians to go to work in an industrial zone. Only a handful of Palestinians were able to use it, however, because of a bureaucratic snafu.
A military spokesman said up to 1,000 Palestinian workers had been expected to pass through the Erez crossing, but the failure of Israeli employers to provide necessary paperwork confined the flow to around 20.
Before violence erupted four years ago, more than 100,000 Palestinians crossed into Israel every day to work, providing a key source of income for poverty-stricken areas. Israel closed the gates as part of its measures to stop suicide bombers and other attackers, but the restrictions — including dozens of West Bank roadblocks — have decimated the Palestinian economy.
"We have received a number of warnings that terrorists plan to perpetrate attacks," Col. Yoav Mordechai, head of the Gaza District Coordinating Office, told the Post. "We hope they won't take advantage of the situation and the humanitarian assistance offered to the Palestinians in order to carry them out."
Meanwhile, Sharon received a boost for his Gaza withdrawal plan when a leader in the Nissanit settlement said 150 of the community's 310 families have signed a declaration agreeing to relocate to Israel.
Nahum Haddad, a member of Nissanit's town council, said the residents were prepared to leave after parliament officially approves the evacuation.
"We are against the evacuation but if it goes through then we want to leave in an orderly way and stay together," Haddad said. He said he expects the remaining families to sign on over the next several days.
Settler leaders have voiced strong opposition to the withdrawal plan, which would uproot 9,000 settlers from the Gaza Strip and four small West Bank settlements.