Nkunda's fighters surrounded ranger stations at the heart of Virunga at Jomba and Bikenge, 80 km (50 miles) north of North Kivu's provincial capital Goma, early on Monday, conservationists said.

The rebels seized about 30 rifles, looted communications equipment, and forced the evacuation of around 300 rangers, park workers, and their families, leaving the area's gorilla population unprotected, they said.

Park authorities said fighting broke out in the park on Tuesday when government forces attempted to dislodge the rebels, but few details were available.

"Clashes started this morning," Norbert Mushenzi, director of the park's southern sector, told Reuters by phone on Tuesday.

In a statement late on Monday Mushenzi said his rangers -- more than 150 of whom have been killed protecting eastern Congo's national parks during 10 years of violence -- were no longer able to protect Virunga's gorillas.

"If anything happens to the mountain gorillas now there is nothing we can do ... As of today the sector is no longer under my control, and we have been rendered powerless," he said.

KILLED AND EATEN

Nine gorillas have been killed in Congo since the beginning of the year, including two slain and eaten by Nkunda loyalists in January.

"The fate of the mountain gorillas now lies in the hands of Nkunda. And last time the park was occupied by his men we lost two silverbacks (adult males)," Robert Muir of the Frankfurt Zoological Society, which supports the management of Virunga, told Reuters from Goma.

"Each day that passes while these troops occupy their habitat puts the survival of the mountain gorillas at risk," he said.

Of a total population of just 700 worldwide, about 380 mountain gorillas live in eastern Congo, which has been racked by more than a decade of violence.

An estimated 4 million people died in a 1998-2003 war, mostly from war-related hunger and disease.

Historic elections last year aimed to break a regional cycle of conflict stemming in part from neighbouring Rwanda's 1994 genocide of Tutsis, and in his inauguration speech last December Congolese President Joseph Kabila vowed to bring peace to the country's east.

However, fresh fighting has erupted in recent weeks after Nkunda's fighters, mostly Tutsis, withdrew from special brigades set up in a failed bid to reintegrate them into Congo's army.