Israeli Defence Minister Ehud Barak ordered the crossing points into the Gaza Strip to remain shut Wednesday, a day after militants in the salient violated a fragile truce by firing three rockets at southern Israel, reported dpa.
An Israeli Defence Ministry spokesman did not rule out the possibility that the crossings would be reopened on Thursday, but said that would depend on events.
Hamas said the Israel re-closure of the crossing points constituted a violation of the terms of the truce, which went into effect last Thursday at 0300 GMT, ending months of violence between the sides.
"Israel pledged not to close the crossing points and to ease the siege," Hamas spokesman Fawzi Barhoom said in a statement Wednesday.
Israel imposed the blockade on the Gaza Strip in response to near- daily rocket and mortar attacks from the salient at its southern towns and villages It had further tightened the strangle-hold after Hamas seized sole control of the enclave in June last year.
The Islamic Jihad claimed responsibility for the rocket launchings Tuesday, saying they were in retaliation for Israel killing a senior Jihad militant and his roommate in the West Bank city of Nablus earlier in the day.
The West Bank is not covered by the Egyptian-brokered ceasefire.
Hamas, the dominant militant faction, which has controlled the Gaza Strip since routing forces loyal to President Mahmoud Abbas one year ago, said it remained committed to the ceasefire, and has urged other Palestinian factions to honour it.
But at the same time, a senior Hamas leader said Wednesday that the Islamist movement would not turn into policemen in order to enforce the truce.
"Hamas will not maintain the lull in Gaza Strip by force even if the factions breached it," Khalil al-Hayya said.
Under the provisions of the ceasefire, militants are to cease their rocket launchings at southern Israeli towns and villages while Israel is to no longer launch air raids on, and ground raids in, the Gaza Strip.
Israel has also undertaken to ease its blockade of the enclave, but the pace depends on negotiations for the release of an Israeli soldier held captive in the Strip for the past two years.
Gilad Shalit was snatched during a cross-border raid launched from the Strip on June 25, 2006. Hamas, which is holding him, is demanding the release of hundreds of prisoners in exchange for freeing him, but has denied that his release is in any way connected to the truce.
"We will not step back from our demands and we will not give up anything," Osama al-Muzini, a Hamas leader said.
Israel had originally demanded that Shalit's release be part of the ceasefire. On Wednesday Prime Minister Ehud Olmert told the Knesset that he and Egyptian President Hosni Mubarak have agreed that negotiations to secure the freedom of the Israeli soldier would be a "main priority."
Speaking at a rally outside Olmert's official residence Tuesday night, to mark the second anniversary of his son's captivity, Noam Shalit said that said the time for excuses was over.
"You do not have all the time in the world. The time has come to act. It's now or never," he said.
"Gilad's life is in danger. If the foot-dragging continues there won't be anyone left to save," he added.