UPDATE 10-Sudanese troops hunt for rebels in Khartoum

(Updates with fighting, Turabi quote)

By Opheera McDoom

KHARTOUM, May 12 (Reuters) - Sudanese forces hunted for suspected Darfur rebels in Khartoum on Monday after an unprecedented rebel attack at the weekend and detained Islamist opposition leader Hassan al-Turabi before releasing him.

Bursts of gunfire kept Khartoum on edge. It was the first time fighting had reached the capital in decades of conflict between the traditionally Arab-dominated central government and rebels from far-flung regions in the oil-producing country.

Darfur rebel leader Khalil Ibrahim told Reuters he would keep up attacks until President Omar Hassan al-Bashir's government fell. About 65 people were believed to have been killed in the attack that began on Saturday.

"This is just the start of a process and the end is the termination of this regime," Ibrahim, of the Justice and Equality Movement (JEM), said by satellite phone. "Don't expect just one more attack."

Sudan accuses neighbouring Chad of backing the rebels and broke off diplomatic ties with its neighbour on Sunday. Chad's government said on Monday it was closing its border with Sudan.

Chad has denied involvement but political analysts say it may have backed the JEM in retaliation for an attack on the Chadian capital three months ago by rebels it said were supported by the Sudanese government.

Exchanges of fire could be heard on the outskirts of Omdurman, across the Nile from the heart of Khartoum and where fighting raged at the weekend. A shooting incident in central Khartoum sent workers fleeing in panic.