DAKAR, Senegal (AP) — Park rangers in eastern Congo hope to begin searching this week for dozens of mountain gorillas who have not been seen since rebels took control of an area where the critically endangered primates live, officials said yesterday.

Virunga National Park is home to a quarter of the world's estimated 800 remaining mountain gorillas, but rangers had to evacuate the area in May because of heavy fighting between a recently formed rebel group and government forces.

Park director Emmanuel de Merode said he was relieved that the rebels had agreed to allow a team of 45 rangers back into the park to conduct a census. Park officials plan to release their findings next month.

However, the search for the park's gorillas had to be pushed back yesterday because of new fighting.

"We have had to delay 24 hours because of the shelling that took place this morning," he said by telephone from the park. "There is very heavy fighting around the park headquarters."

Earlier this month, family members of rangers were evacuated from the park's headquarters about 50 kilometres (30 miles) from the city of Goma because of security concerns.

More than 130 park rangers have been killed during violent conflicts in eastern Congo in the aftermath of neighbouring Rwanda's 1994 genocide. One attack alone last year left three park rangers and five Congolese soldiers dead.

In 2007, the fragile habitat in the Central African highlands also became off-limits for more than a year because of violence, though a subsequent census later found that the park's gorilla population had grown during that period.

A myriad of militias and rebel groups plague mineral-rich eastern Congo, and the violence intensified earlier this year with the formation of a new group calling itself M23. The fighting has forced more than 200,000 people from their homes since April.