KAMPALA, Uganda — Ugandan President Yoweri Museveni plans to sign into law a bill that prescribes life imprisonment for some homosexual acts, officials said Friday, alarming rights activists who have condemned the bill as draconian in a country where homosexuality already has been criminalized.

Museveni announced his decision to governing party lawmakers, said government spokesman Ofwono Opondo. In Twitter posts on Friday, Opondo said the legislators, who are holding a retreat chaired by Museveni, “welcomed the development as a measure to protect Ugandans from social deviants.”

Museveni’s decision was based on a report by “medical experts” presented at the retreat, saying that “homosexuality is not genetic but a social behavior,” said Opondo.

Evelyn Anite, a spokeswoman for the governing party, said the report, which had been requested by the president, was prepared by more than a dozen scientists from Uganda’s Health Ministry.

Opondo and Anite both said the president did not indicate when he will sign the legislation into law.

Homosexuality already is illegal in Uganda under a colonial-era law that criminalizes sex acts “against the order of nature.”

An earlier version of the bill, first introduced in 2009, proposed the death penalty for some homosexual acts. Although that provision was later removed amid international pressure, rights groups want the whole bill jettisoned. Amnesty International has described it as draconian, repeatedly urging Museveni not to sign it into law.

But the bill is popular in Uganda, one of many sub-Saharan African countries where homosexuals face severe discrimination if not jail terms. A new law in Nigeria last month increased penalties against gays.

The bill before Museveni would, among other things, make conducting a same-sex marriage ceremony punishable by seven years in prison.