JERUSALEM (Reuters) - Militants in the Gaza Strip fired a rocket into Israel on Wednesday for the first time since a Palestinian unity government was formed, prompting strong Israeli condemnation of President Mahmoud Abbas.

After past rocket attacks, Israel has said it holds Hamas, which has ruled the Gaza Strip since 2007, responsible, and frequently responds with air strikes on militant positions there.

Israel gave no indication it planned to take any punitive action against Mr Abbas' West Bank-based Palestinian Authority, and there was no immediate claim of responsibility for the rocket strike, which caused no casualties or damage.

But it said that now that the Western-backed Mr Abbas had sworn in a government supported by Hamas Islamists in the Gaza Strip, he needed to take more action to prevent cross-border attacks.

The official Palestinian WAFA news agency said Mr Abbas condemned the attack and called on all Palestinian factions to hold their fire and "not give Israel any pretext" to strike in the Gaza Strip.

Mr Mark Regev, a spokesman for Israeli Prime Minister Benjamin Netanyahu, said Abbas's condemnation was "nothing but empty rhetoric".

In an e-mailed statement, Mr Regev said: "President Abbas claims that the new Palestinian government honours all previous commitments. So why has he not disarmed the terrorist organisations in Gaza as he is obligated to do?"

After the unity government was formed last week, Mr Abbas pledged its continued commitment to existing interim peace deals with Israel. Israel said the administration was a front for Hamas, a group that advocates its destruction, and suspended peace negotiations with the Palestinian leadership.