Hamas has rejected calls by Palestinian leader Yasser Arafat for militant groups to renew the truce they abandoned last week.
Hamas ended a seven-week-long truce last week
Hamas political leader Abdel Aziz al-Rantissi said the group would not consider a truce while Israel continued targeting its followers, and warned against any attempt at a crackdown by Palestinian security forces.
Palestinian Foreign Minister Nabil Shaath told the BBC that by rejecting Mr Arafat's appeal the militants were putting Palestinians "in danger".
"The roadmap is the only proper road we have back to peace," he said.
On Thursday a makeshift rocket fired by Hamas landed in an industrial zone in the
coastal city of Ashkelon, near the Gaza
Strip, the Israeli army said.
The attack caused no casualties or damage but has raised tensions in the area; Israel has said it will retaliate for the rocket fire.
Hamas and Islamic Jihad both called off a seven-week-old truce last week after Israel killed Hamas co-founder Ismail Abu Shanab in retaliation for the suicide bombing of a Jerusalem bus that left 21 people dead.
On Wednesday, Mr Arafat called on all factions to sign up again to the truce in a bid to salvage the US-backed peace roadmap.
Mr Arafat accused Israel of rejecting the roadmap by "escalating" attacks against Palestinian militants.
But Israel dismissed Mr Arafat's ceasefire call as propaganda, and said it would continue targeting militants until the Palestinian Authority dismantled their organisations.
Raanan Gissin, an adviser to Israeli Prime Minister Ariel Sharon, said Mr Arafat's statement was meaningless: "Arafat has never stopped supporting the strategy of terror. He has no interest in a peaceful solution."
The White House also dismissed the move, saying: "Arafat has once again shown himself to be part of the problem. He is not part of the solution."
Hamas 'ready to talk'
The BBC's David Chazan, in Gaza, says few Palestinians believe that the Palestinian Authority will act against the militants while Israel continues to target them.
They say that if the militant groups are to be dismantled, then Israel must at the same time start dismantling its settlements in Gaza and in the West Bank, our correspondent says.
On Wednesday Mr Abbas held emergency cabinet talks in the Gaza Strip about the escalating violence between Israel and Palestinian militants.
Mr Rantissi said Hamas was only "ready to talk" with Mahmoud Abbas, also known as Abu Mazen, who broke off all contact with hardline groups amid escalating violence.
Our correspondent says Mr Abbas is being blamed by the Americans and the Israelis for not doing enough to stop the violence.
But he says the prime minister has precious little support from Palestinian public opinion.