The Palestinian Authority (PA) in the West Bank and Hamas in the Gaza Strip continued their back-and-forth arrests of top party leaders Friday, capping a week of detentions sparked by a car explosion in the Gaza Strip that killed five Hamas militants and a girl.

Hamas blamed Fatah for the blast; Fatah said the explosion was due to internal conflicts within the Islamist organization.

Although President Mahmoud Abbas told his security forces Thursday night to free all Hamas supporters taken in the West Bank over the past week, sources close to the detained activists told Deutsche Presse-Agentur dpa on Friday morning that they were unaware of anyone being released.

On the contrary, they said, more arrests were made overnight, with PA forces arresting Muhammad Ghazal, a member of Hamas leadership council, and many other Hamas leaders and supporters in the West Bank Thursday and Friday morning in a campaign that came in response to Hamas arrest of dozens of Fatah members in the Gaza Strip.

At the same time, PA and Fatah said the de facto Hamas government in the Gaza Strip arrested top Fatah leaders in the salient early Friday morning.

Those arrested included including Zakaria al-Agha, the highest ranking Fatah official in the Gaza Strip and member of its Central Committee, as well as Ibrahim Abu al-Naja, a senior Fatah official, and many other Fatah leaders.

Hamas said in a statement Friday that 'the arrest of Fatah leaders in Gaza came in response to the arrest of Hamas leaders in the West Bank.'

It said, 'Fatah should know that the arrest of top Hamas leaders including Muhammad Ghazal, council, is like playing with fire and Abbas' release of our leaders will end this problem.'

The two movements have been at loggerheads since Hamas defeated Fatah in the January 2006 parliamentary elections in the Palestinian territories. The tensions came to a head in June 2007 when Hamas gunmen routed forces loyal to Abbas to seize control of security installations in the Gaza Strip.

Abbas retaliated by pulling Fatah out of a Hamas-led unity government and by dismissing Hamas leader Ismail Haniya from his post of premier.