The Congolese Army launched an operation on Friday night to pursue an unidentified militia group who kidnapped two British tourists gorilla trekking in one of the world’s most dangerous national parks.

Armed men opened fire on a convoy of vehicles shortly after it entered the Virunga National Park in the east of the Democratic Republic of the Congo on Friday morning, according to wildlife officials.

A female Congolese park ranger was killed before the two Britons, who have not been named, were seized by the gunmen, the Congolese Institute for Nature Conservation, which employed the warden, confirmed.

A third occupant of the vehicle, believed to be the Congolese driver, was shot in the shoulder before either being released or managing to escape, according to a security source working with a western charity in the east of the country.

The two Britons are both male, according to an official at the park. He said the captors, while unknown, were demanding a ransom of $200,000 for their release.