Hamas security forces arrested the spokesman for Fatah's Aksa Martyrs Brigades in the Gaza Strip on Sunday.

Muhammad Abu Armaneh, who is better known by his nom de guerre Abu Qusai, was taken into custody while standing in front of his shop in Rafah, sources in the Gaza Strip said.

The arrest is believed to be linked to Hamas's attempts to enforce the truce agreement that was reached with Israel last week.

Last week, Armaneh was the one who announced that the Aksa Martyrs Brigades had fired three rockets at Israel in violation of the cease-fire.

The rocket attacks drew sharp criticism from Hamas, whose leaders threatened over the weekend to arrest anyone who violates the cease-fire, even if he belonged to Hamas.

Fatah officials reacted with anger to the arrest of Armaneh, who is one of the most senior members of the Aksa Martyrs Brigades in the Gaza Strip.

He also played a major role as spokesman for the Brigades during the first years of the second intifada, which began in September 2000. He has been on Israel's list of wanted terrorists for many years.

Fatah legislator Ashraf Juma'a strongly condemned the arrest and urged Hamas to release him immediately and unconditionally. He said that Israel was the only party to benefit from the increased divisions between Fatah and Hamas.

Juma'a also emphasized the need to abide by the cease-fire and called on the Aksa Martyrs Brigades to refrain from firing rockets at Israel.

Armaneh was arrested shortly after Hamas announced that the Brigades would no longer be treated as part of a legitimate political party, a move that paves the way for taking measures against its members.

The Aksa Martyrs Brigades accused Hamas of kidnapping its spokesman and warned against harming him. "The kidnapping of Abu Qusai and other members of the Palestinian resistance groups by Hamas only serves the interests of Israel," the group said in a statement. "This also proves that the cease-fire that Hamas reached with Israel is tantamount to national treason because the agreement allows Israel to continue targeting Palestinians in the West Bank."

Zakaria Zubeidi, the Jenin commander of the Aksa Martyrs Brigades, issued a statement in which he called on Hamas to release Armaneh within 12 hours or face the consequences. "It's become impossible to remain silent in the face of Hamas's crimes against our people," he said. "If they don't release him within 12 hours we will hold all Hamas leaders in the West Bank responsible."