Israel said at least six rockets were fired, causing minor damage but no injuries as the Jewish state celebrated its Independence Day.
Amir Peretz, Israel's defence minister, warned the Palestinian government against allowing more attacks while the Palestinian president urged Israeli restraint.
'Exception'
"The violation of the truce is an exceptional event that will not last," Mahmoud Abbas said in Rome.
"I take this opportunity to appeal to Israel to show the necessary self-control so that this will not happen again."
The Palestinian government, which Abbas's Fatah faction jointly runs with Hamas, called for the ceasefire to remain in place.
"The government is interested to keep the ceasefire and the calm and we are trying, through consultation and discussion with the Palestinian factions, to take a position in order to protect our people," government spokesman Ghazi Hamad said.
Israel Radio reported that Ehud Olmert, Israel's prime minister, was to meet his senior security advisers on Wednesday to consider their options.
Egyptian security officials in Gaza planned to meet the Brigades and other armed groups to try to head off any further escalation.
Bloody weekend
Tuesday's attacks marked the first time that Hamas claimed responsibility for launching rockets into Israel since a November 26 ceasefire took effect between the army and Palestinian fighters.
Abu Obaida, a spokesman for the Brigades, said "the truce no longer exists".
"It's the Israeli enemy that has not respected it, and now it's the turn of Palestinian groups," he said.
Observers say there has been a debate within the Hamas leadership over whether the group has to take a harder line towards Israel, but the group denies any divisions.
Abu Obaida told Al Jazeera: "There is no co-ordination between the military [wings] of the Palestinian resistance faction and the government or the [Palestinian] Authority."
He said the attack was in response to the death of nine Palestinians, two teenagers and five fighters among them, by Israeli troops over the weekend in the occupied West Bank and Gaza.
The deaths marked the bloodiest weekend of Israeli-Palestinian violence since the November truce and sparked calls for retaliation on the part of Palestinian armed groups.
Under the terms of the November ceasefire, the Israeli army withdrew troops from the Gaza Strip and Palestinian fighters there were supposed to halt rocket fire.
Until Tuesday, the truce had largely held despite violations by both sides.