Palestinian leader Mahmoud Abbas has sacked the overall commander of Palestinian forces following mortar attacks on Israeli settlements.
Hamas' rockets damaged property but did not cause any casualties
Gen Abdul Razek Majaidie lost his job along with national police chief Saeb al-Ajez and another senior official.
The dismissals are "punitive measures" against officers who failed to do their duty, a spokesman for Mr Abbas said.
Hamas militants said they carried out the attacks in retaliation for the death of a man killed by Israeli fire.
An Israeli military source said soldiers had suspected a militant infiltration and fired warning shots.
Israel has warned that if Mr Abbas cannot stop the attacks, it may take action against the militants, despite agreeing to a ceasefire earlier this week.
Hamas has said it is not bound by the agreement.
Mr Abbas on Thursday ordered his security forces to prevent a repeat of the 30-shell mortar attack, which caused damage but no injuries in the Gush Katif settlement in southern Gaza.
Mr Abbas gave "strict instructions" to prevent further threats to the ceasefire he agreed with Israeli Prime Minister Ariel Sharon in Egypt.
He is to travel to Gaza on Friday to tell the militants he will not tolerate any more violence, Palestinian cabinet official Hassan Abu Libdeh told the Associated Press news agency.
The BBC's Alan Johnston in Gaza says Mr Abbas was under pressure to respond to the attacks on the settlement and he has reacted by sweeping away individuals at the very top of his security apparatus.
Palestinian officials said Israel postponed security talks on Thursday as a result of the mortar attack, but Israel said no talks were scheduled.
Alongside the continuing attacks on Israel, our correspondent says the new Palestinian leadership faces internal law and order problems - as highlighted by a militant raid on a Gaza prison on Thursday morning, that left three prisoners dead.
Thursday's attack was the first by Palestinian militants since Mr Abbas and Mr Sharon declared an end to four years of violence at a summit in Egypt.
A spokesman for the militants told the Reuters news agency they had "initiated calm" as Mr Abbas had requested, but would not "stand handcuffed" in the face of Israeli aggression.
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
Hamas says it will decide whether to join the ceasefire only after it has judged to what extent the Israelis are complying with their side of the agreement.
Meanwhile, Mr Sharon told Israeli newspaper Haaretz on Thursday that he would be prepared to release some Palestinian prisoners convicted of attacking Israelis.
Mr Abbas made the issue a priority during the Sharm al-Sheikh summit.
Mr Sharon said certain prisoners could be freed if the proposed Israeli withdrawal from Gaza went smoothly.
Israel has previously refused to release Palestinians convicted of violent attacks.