Anna Friel is to help publicise a newly invigorated campaign against plans to explore for oil in one of the world's most important regions for wildlife.

British-based oil and gas company Soco began aerial surveys of the Virunga National Park in the Democratic Republic of Congo this month, despite pleas from environmental campaigners and the British government.

Friel flew to neighbouring Uganda earlier this year to make a documentary about the plight of the remaining 700 mountain gorillas in the region. The short film, Virunga, made to support the WWF's Draw the Line campaign, will be shown in Odeon cinemas throughout October.

The actress travelled with her eight-year-old daughter, Grace, to witness the wildlife around Lake Victoria and Lake Edward, where some of the proposed oil exploration would take place. This corner of Uganda and the DRC contains some of the richest wildlife on Earth, while also supporting a population afflicted by war and poverty. The balance is a tenuous one.

More than 30,000 fishermen rely on Lake Edward in Virunga for their livelihoods and there are fears that any contamination of the lake, a vital source of water and protein as well as one of the sources of the Nile, could have a huge impact.

"My experience of Africa before this journey with WWF was so different to anything I could have imagined this place to be," Friel told the Observer. "The landscape was the most breathtaking I have ever experienced and the wildlife – gorillas, hippos, elephants, birds – seemed more beautiful than any creatures I had seen before, perhaps because there was such a vulnerability with all the threats facing them."

She said she was deeply affected by meeting local people. "One of the most moving experiences of my time in Uganda was visiting a fishing village within Queen Elizabeth national park and therefore benefits from the tourist trade. The fishermen didn't know anything about oil exploration and the devastating effect it could have on the lake that provides their family's livelihood. It is the people as well as the wildlife who rely on Lake Edward and its surrounding areas, and this could be so easily taken from them."

You can join the campaign at wwf.org.uk/virunga