Gay rights groups in Cameroon have gone on strike, refusing to continue work on Aids programmes until foreign donors improve security.

The groups say their work puts them at risk of murder and attack, and have written to donors asking them to provide protection.

"We have all decided to stop our work in the field because our security is at risk," said Yves Yomb, executive director of Alternatives-Cameroun, which works to fight Aids in Cameroon. "We have no protection from the police and we feel that our lives are at risk."

The groups have sent a letter to Global Fund, the international financing organisation that works to prevent and treat Aids, and other donors.

"[Cameroon's] long-decried climate of homophobia has intensified and now has reached a critical point," the letter states.

"The pursuit of our various missions requires a minimum level of security, institutional support and financial support."

The letter comes one week after prominent activist and journalist Eric Lembembe was found dead, believed to have been killed for his work campaigning for gay rights in Cameroon, where homosexuality is illegal.

This week two gay men were prosecuted for homosexual activity, the latest in a string of convictions in the country, where campaigners say attacks and persecution of openly gay people are common.

Human rights groups have called on the government to decriminalise homosexuality, and accuse it of failing to speak out against Lembembe's murder.

"[The murder of Eric Lembembe took] place in a general homophobic context of complicit silence from Cameroonian officials despite numerous incidents targeting individuals and organisations defending sexual minorities' rights," 11 rights organisations said, in a letter to the Cameroon president, Paul Biya.

"Religious leaders – the Catholic church in particular – publicly condemn homosexuality and incite protests against the issue."

There has been intense debate about gay rights in Africa, where homosexuality is illegal in 38 countries, and punishable by death in four.

Last month, Barack Obama caused controversy in many African nations when he used a tour of the continent to urge countries not to discriminate against gay people, saying: "I believe that everybody has to be treated equally."

Cameroon's government has denied that it does not protect gay people, releasing a statement last week that it was investigating Lembembe's death.

"We hope that the authorities are serious," said Yomb. "But until we see something concrete, we do not feel protected. That is why we have asked the Global Fund to negotiate our security with us, so that we can continue working in the field."

The Global Fund said it strongly condemned attacks on gay rights activists, and was considering the request.