Kampala, Uganda - Gay rights supporters are denouncing Ugandan lawmakers for voting to criminalize anyone who publicly identifies as a sexual minority or engages in same-sex activities.

The bill, which Uganda's parliament passed late Tuesday with only one dissenting voice, will become law if President Yoweri Museveni signs it as expected.

In a statement, Tigere Chagutah, regional director of Amnesty International in East and Southern Africa, said the Anti-Homosexuality Bill amounts to a grave assault on LGBTQ people and is contemptuous of the Ugandan constitution.

Penalties in the bill include 20 years in prison for so-called promotion of homosexuality and child recruitment, while 'attempted homosexuality' calls for 10 years in prison.

The bill prescribes the death penalty for anyone who forces children, people with disabilities, people with mental illness and those of advanced age into an act of homosexuality.

Roland Ebole, an Amnesty International regional researcher, said the bill, if signed into law, will encourage anti-LGBTQ activity.

'And it is very vague in terms of what this promotion is when it says promotion of homosexuality,' Ebole said. 'This provision will encourage homophobia, it will encourage discrimination, and will discourage human rights advocates and [nongovernmental organizations] from carrying out their work.'

Three hundred and eighty-nine lawmakers attended Tuesday's debate and final passage of the bill - a show of support meant to ensure the act does not face the same fate as a previous Anti-Homosexuality Bill that was annulled due to an inadequate turnout in parliament.

The speaker quickly took a roll call to ensure a quorum was attained.

Legislator Charles Onen attempted to bring humor to the debate in his speech.

'Right honorable speaker, when I look at you and the honorable ladies in this House, there's no reason for a man to run after a man for sex,' he said. 'Right honorable speaker, there's nothing so sweet and so good for a man more than a woman.'

Legislator Fox Odoi was booed as he presented a minority report that said the bill was misconceived and the current penal code act was sufficient to deal with matters related to homosexuality.

'It was introduced during a time when anti-homosexual sentiments have been whipped up across the country and is not based on any factual or evidential value to show incidents of homosexuality have increased and require additional legislation,' he said. 'Right honorable speaker, according to the annual crime police reports, incidents of homosexuality have been reducing in Uganda.'

After six hours of debate, the bill was passed with legislators singing the national anthem in celebration.

Parliament now awaits Museveni's veto or signature.

The U.N. High Commissioner for Human Rights, Volker Türk, called on Museveni on Wednesday not to sign the bill, which he described as among the worst of its kind in the world and a deeply troubling development.