Fierce fighting in Gaza kills 34 more
They have also taken control of several other buildings.
Prime Minister Ismail Haniyeh's home has been attacked for the second day in a row and four mortar shells slammed into the office of President Abbas in Gaza city.
Witnesses say it is the bloodiest day of factional violence in Gaza in last 18 months.
The violence threatens to unravel Palestinian national unity government.
Fatah leaders have decided to pull out from the three-month-old Hamas-led government until the violence ends.
Palestinian President Mahmoud Abbas is accusing his Hamas rivals of staging a coup as violence escalates in Gaza. He will meet senior members of his Fatah movement later to discuss a response to the deadly fighting.
The UN Secretary general, Ban Ki-moon, has called for support for President Abbas' efforts to end fighting in Gaza.
Meanwhile, a Russian citizen, Dr. Sami Abu Snimh, is among several men detained in Gaza in Israeli raids. His wife Elena has applied to the Russian Embassy for assistance in securing her husband's release.
Dr. Snimh’s cousin Abu Salim said he was not involved in any political activity adding that Israeli troops arrested him without any explanation.
“He studied medicine in Russia to help Palestinian people. He is not involved in any political or criminal activity. And they just raided his house and arrested him. We still don’t know why! More than 50 people have been released, but five, including my cousin, are still under arrest. We appeal to the world to help free him,” Mr Abu Salim noted.