At least four people were hurt on Sunday after armed men purportedly from al-Aqsa Martyrs Brigades stormed the ministry in Gaza City, where they were confronted by Hamas guards, ministry officials said.
But a spokesman for the brigades, which is affiliated to the Fatah, denied the men were from the faction. He said they were from a Gaza clan affiliated with Fatah.
The guards from the Izz al-Din al-Qassam Brigades chased off most of the intruders and captured four of the men, tying them up and putting them into a police car as people in the street cheered, witnesses said.
Khaled Abu Hillel, a spokesman for the interior ministry, said: "The time has passed when our institutions and our police can be attacked. Whoever holds a gun against one of our institutions, or one of our policemen, opens himself for death."
Meanwhile, in the West Bank city of Bethlehem the Israeli occupation army killed two Palestinians after firing on a car.
Palestinian security sources said one of the dead men was a member of the Palestinian security forces.
A member of Fatah at a rally
against Hamas in the West Bank
An Israeli army spokeswoman said the men killed on Sunday in Bethlehem, which lies near Jerusalem, were wanted for attacks against soldiers and for firing on Jewish settlements.
"We had accurate intelligence on the identity of the vehicle and the forces in the area even knew the number plate of the car," she said, adding the men fired at soldiers from their car.
Mushir al-Masri, a Hamas politician, condemned the killings. "We warn that the continuation of such an escalation will lead to an explosion in the region," he said.
Also on Sunday, in a show of force hundreds of armed Palestinian security men in uniform marched through the town of Jenin in the occupied West Bank in support of Mahmoud Abbas, the Palestinian president, and Fatah.
The Gaza Strip has seen growing lawlessness in recent years among members of rival armed groups. Hamas and Fatah, however, has rarely engaged in violent confrontations.
Sunday's clashes came a day after about 20 people were hurt in armed confrontations in Gaza between students and fighters from the two rival movements, Hamas and Fatah. It was the most serious fighting between Palestinians since Hamas won a parliamentary election in January.
The violence on Saturday erupted after the condemnation by exiled Hamas political leader Khalid Mishaal of Abbas' veto of a new Gaza security force formed by the group and headed by a resistance group commander.
The appointment of Jamal Abu Samhadana, head of the Popular Resistance Committees which has often attacked Israel, as leader of the new Gaza police force was seen as an attempt by Hamas to strengthen its grip on the Interior Ministry.
"The two parties have agreed to call on our people to stop all forms of tension and to cement national unity"
When Abbas cancelled the decision, Mishaal said it assisted a Western campaign to isolate the Palestinian government.
Later on Saturday, Egyptian officials tried to mediate an end to the Hamas-Fatah tensions.
A spokesman for Fatah, Mahar Meqdad, said after a meeting between the two groups: "The two parties have agreed to call on our people to stop all forms of tension and to cement national unity."
Hamas and Fatah officials did not elaborate on what steps would be taken.
Plea for unity
Mishaal said after the violence on Saturday that Hamas respected Abbas' authority and called for Palestinian unity.
The interior ministry said the new Gaza force would work from within the existing security establishment, headed mainly by Fatah loyalists.
But Abbas' aides said only the Palestinian president could make decisions regarding the government.
Hamas has rejected Abbas' calls to pursue a negotiated peace with Israel.