Abbas gave "strict instructions" after the Gaza attack

Militant group, Hamas, said it fired mortars and rockets at the Gush Katif settlement to avenge the death of a Palestinian man on Wednesday.

Mr Abbas gave "strict instructions" to prevent further threats to a ceasefire he agreed with Israel on Tuesday.

Hamas has said it is not bound by the ceasefire agreement.

Palestinian officials said Israel postponed security talks on Thursday as a result of the mortar attack, but Israel denied talks were scheduled.

Egypt accord

The Hamas attacks started at about 0300 local time (0500 GMT) and lasted several hours.

Hamas said it fired nearly 50 missiles, but the Israeli army said it had registered only about half that number.

Abbas told me simply that [prisoner release] is a major problem Ariel Sharon, Haaretz interview Hamas' manoeuvres Q&A: Sharm summit

A house was damaged but there were no injuries.

Hamas said it was avenging the death of a Palestinian man shot by Israeli troops as he walked near the Atzmona settlement in southern Gaza.

An Israeli military source said soldiers suspected a militant infiltration and fired warning shots.

Thursday's attack was the first by Palestinians since Mr Abbas and Israeli premier Ariel Sharon declared an end of four years of violence at a summit in Sharm al-Sheikh, Egypt, on Tuesday.

Hamas had said it would decide whether to join the ceasefire only after it had judged to what extent the Israelis were complying with their side of the agreement.

A senior Palestinian official said Thursday's attacks had led Israel to postpone security talks expected to cover the Israeli release of Palestinian prisoners and issues relating to Israel's withdrawal from some Palestinian areas.

However, a spokesman at the Israeli prime minister's office denied any talks were scheduled for Thursday.

Ranch meeting

Mr Abbas is scheduled to meet militant groups in Gaza later on Thursday to try to persuade them to adhere to the ceasefire.

He said he was considering an unspecified series of "decisions and measures" if Thursday's violence was repeated.

Mr Sharon is holding a cabinet meeting to brief ministers on the outcome of the Sharm al-Sheikh summit.

The two leaders are then due to meet again before Tuesday at Mr Sharon's Sycamore Ranch in southern Israel.

Mr Sharon said in a newspaper interview on Thursday that he would be prepared to release some Palestinian prisoners convicted of attacking Israelis.

INTIFADA TOLL 3,225 Palestinians killed by Israelis (3,135 by military in the occupied territories, 54 by military inside Israel, 34 by settlers in the occupied territories) 950 Israeli killed by Palestinians (431 inside Israel, 218 settlers, 218 soldiers on duty in the occupied territories Source: B'tselem Intifada timeline

Mr Abbas had made the issue a priority during the Sharm al-Sheikh summit.

Mr Sharon told the Haaretz daily Israel would free certain prisoners if the proposed Israeli withdrawal from Gaza went smoothly.

Israel has previously refused to release Palestinians convicted of violent attacks.

The Egypt summit was the highest-level discussion between the two sides since the Palestinian intifada (uprising) began more than four years ago.