Hamas warned its Fatah rivals on Tuesday that a crackdown against the Islamist group by forces loyal to Palestinian President Mahmoud Abbas could spark a revolt in the occupied West Bank.

A senior Palestinian security official in Ramallah dismissed the threats by "irresponsible people".

Abbas's security forces have detained at least 150 Hamas supporters in the West Bank in response to a sweep in the Gaza Strip, where Hamas seized nearly 200 Fatah sympathizers after a bomb blast killed five Hamas militants and a girl on Friday.

Hamas blamed the bombing on Fatah, which denies involvement.

In Gaza City, Hamas spokesman Sami Abu Zuhri said the crackdown in the West Bank could trigger a revolt.

"This will only lead to a new uprising against the (Israeli) occupation and its security agents," he said in a mocking reference to Abbas's Palestinian Authority forces.

Hamas often taunts Abbas and Fatah for their commitment to U.S.-sponsored peace talks with Israel, which controls the West Bank, while allowing a role for Palestinian security forces.

"Now the Zionists (Israelis) are protecting you," Hamas said in a separate statement addressed to security forces in the West Bank. "You know that once the protection of the Zionists is over, people will enter your headquarters and kick you out." 

UNHEALED RIFT

Hamas fighters routed their Fatah foes in the Gaza Strip a year ago, when hundreds of people were killed during and after the fighting. The Islamists have not tried to replicate their conquest in the West Bank, but have rejected Abbas's demands that they relinquish control of Gaza before any reconciliation.

The West Bank security official said of Hamas's threats: "If they can take these headquarters, what are they waiting for? Why is it allowed for them to kill and arrest people in Gaza?"

The official, who asked not to be named, said the measures targeted illegal weapons and lawbreakers, not Hamas. "Many Hamas figures who abide by the law are not arrested," he said.

He would not say how many people had been arrested since Friday, but said many detainees had been released. Hamas also says it has freed about half of those it had rounded up.

However, jails were overflowing in the West Bank city of Jenin, where a Palestinian security source said the arrest campaign had slowed because there was no more room in the cells.

He said at least 70 suspected Hamas supporters had been detained in Jenin alone.

Palestinian security forces released a political science lecturer at al-Najah University in Nablus, but Hamas said 53 of its supporters were still behind bars in the West Bank city.

"Freedom of speech should be honored. Otherwise there will be a social and political rift among Palestinians," the lecturer, Abdul Sattar Qasem, told Reuters after his release.

Qasem, 60, describes himself as an independent, but some Fatah officials see him as pro-Hamas. He said the officer who detained him on Sunday night gave no reason for the action.

Qasem said he was not mistreated during the 24 hours he spent in a cell with 12 other detainees.

Both Fatah and Hamas have mistreated and sometimes tortured detainees in the past year, human rights groups say.