Palestinian President Mahmoud Abbas on Saturday declared Hamas' paramilitary militia in the Gaza Strip illegal, raising the stakes in his standoff with the Islamic movement that controls the Palestinian parliament and Interior Ministry.

Hamas retaliated by saying it would double the size of the Hamas militia in the Gaza Strip.

Interior Ministry spokesman Khaled Abu Hilal said the unit would be doubled to 12,000 members. He said Interior Minister Said Siyam made the decision "in view of the ongoing security deterioration."

Abbas' announcement came two days after members of the Hamas force attacked the home of a senior security commander in Gaza, killing the man and seven of his bodyguards. The man was a member of the Preventive Security force, which is loyal to Abbas' Fatah party.

In retaliation, gunmen attacked Hamas officials in two separate incidents in the West Bank on Saturday.

In the first incident, gunmen stopped the car of Nablus' deputy mayor, Mahdi al-Khamdali, pulled him out and took him away in a separate car, security officials said. Al-Khamdali is a member of Hamas. There was no immediate claim of responsibility, but the officials said they believed the kidnappers were supporters of the rival Fatah group.

In the West Bank town of Ramallah, meanwhile, gunmen stormed the offices of the Hamas-controlled Interior Ministry, shot the office manager in the legs and took him away, Palestinian security officials said. The man, also a Hamas supporter, was released in a nearby town and hospitalized, the officials said.

More than two dozen people have been killed in a month of factional fighting between Hamas and Fatah. The fighting has been confined almost entirely to the Gaza Strip, but unrest has spread to the West Bank in recent days.

Abbas' office said the decision was made "in light of continued security chaos and assassinations that got to a number of our fighters ... and in light of the failure of existing agencies and security apparatuses in imposing law and order and protecting the security of the citizens."

Fatah and Hamas have been locked in a power struggle since the Islamic group defeated Fatah in parliamentary elections a year ago. The dispute has centered around control of the powerful Palestinian security forces.

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With Abbas, who was elected in a separate presidential vote, claiming authority over most of the security forces, Hamas last year formed its own unit, known as the "Executive Force."

Members of the black-clad Hamas militia are visible throughout Gaza, and have periodically clashed with the existing pro-Fatah security forces.

Hamas spokesman Fawzi Barhoum called Abbas' announcement Saturday "misplaced and useless."

More than two dozen people have been killed in the latest wave of factional violence, which erupted early last month. Thursday's attack on the Fatah commander's home in northern Gaza was the bloodiest single battle in the standoff to date.

Abbas agreed in recent months to integrate the Hamas unit into existing security forces, but those efforts have failed to make progress.

In his statement Saturday, Abbas reiterated the offer but said he would not wait forever. "It will be dealt with accordingly so long as it is not immediately folded into the legal security forces," Abbas said.