The Archbishop of Canterbury has urged the government to offer protection to gay and lesbian people seeking asylum in the UK after the "profoundly shocking" killing of a Ugandan gay rights activist this week.

Dr Rowan Williams, who is in Dublin for the Primates Meeting, joined the US Secretary of State, Hilary Clinton, in calling for greater protection of sexual minorities and said there was a need to secure the safety of those seeking asylum.

David Kato was murdered at his home in Mukono, Kampala, weeks after winning a court victory over a tabloid that called for homosexual people to be hanged.

His murder came as a lesbian due to be deported from Britain to Uganda said she feared she would be killed if forced to return. Brenda Namigadde – who fled Uganda in 2003 after being threatened over her relationship with her Canadian partner – is being held at Yarl's Wood detention centre.

She told the Guardian: "I'll be tortured or killed if I'm sent back to Uganda. They've put people like me to death there. Most of my friends in Uganda have disappeared."

Her initial asylum claim was rejected, in part on the basis that there was not sufficient evidence that she is a lesbian.

Dr Williams said: "Whatever the precise circumstances of his death, which have yet to be determined, we know that David Kato Kisule lived under the threat of violence and death.

"No one should have to live in such fear because of the bigotry of others. This event also makes it all the more urgent for the British government to secure the safety of LGBT asylum seekers in the UK.

"This is a moment to take very serious stock and to address those attitudes of mind which endanger the lives of men and women belonging to sexual minorities."

Ugandan society is hostile towards gay people but rhetoric from religious leaders and politicians has made it worse. The Anglican Archbishop of Uganda, the Most Rev Henry Orombi, has repeatedly said that homosexuality is incompatible with the word of God, while a bill calling for gay people to be imprisoned for life remains before parliament.

Kato was one of those leading the fight against the proposed legislation, which drew international condemnation when published in 2009.

Archbishop Orombi, who opposed the anti-homosexuality bill but has been outspoken in his opposition to homosexuality, gay clergy and same-sex blessings, has yet to comment publicly on Kato's murder.