Cairo - The headquarters of Egypt's opposition al-Ghad party were set on fire on Thursday amid clashes between rival factions in the party, security sources told the Deutsche Presse-Agentur, dpa.

Twelve fire trucks were called in to extinguish the flames in the party's offices in downtown Cairo.

The clashes involved supporters of the party's chief Ayman Nour and his deputy Moussa Moustafa Moussa, in their ongoing dispute over who should lead the party. The dispute has been going on since September 2005.

Nour was sent to prison in late 2005 on forgery charges after coming second to Egyptian President Hosni Mubarak in the last presidential elections. Many people believe that Nour was sent to prison merely for trying to challenge Mubarak in the elections.

Moussa's backers said that they raided the office when Nour's supporters refused to leave the building.

"We had a court ruling that gives us the right to take over the office," one Moussa supporter claimed.

Nour's backers threw Molotov cocktails to stop the raid.

Meanwhile, Jameela Ismail, Nour's wife and a prominent party member, said that the attackers hit the office's windows with rocks and shot fire on the door.

Police arrested eight of Nour's supporters. The group chanted anti-Mubarak slogans during their arrest, the sources said.

"These people are backed by the Egyptian ruling party who are trying to stop any opposition movement," Ismail told (dpa)