The United Nations human rights chief has given her reaction to Nigeria’s anti-gay law by describing it as unprecedented for its multiple violations of basic freedoms.

It comes as reports say that dozens of gay men have recently been arrested in the country.

Nigerian President Goodluck Jonathan quietly gave assent to the Same-Sex Marriage Prohibition Act earlier this month, but news only emerged on Monday.

According to the law, anyone who enters into a same-sex marriage, civil union or domestic partnership could face up to 14 years in prison. Additionally, same-sex marriages legally performed in other countries would be considered void by the Nigerian Government.

The law also restricts LGBT citizens from meeting in public settings.

US Secretary of State John Kerry issued a strong statement condemning Nigeria’s actions. “It is inconsistent with Nigeria’s international legal obligations and undermines the democratic reforms and human rights protections enshrined in its 1999 Constitution,” Mr Kerry yesterday.

The UK’s Foreign and Commonwealth Office also criticised Nigeria on Tuesday, saying “the Nigerian Government is aware of our concerns”. 

“Rarely have I seen a piece of legislation that in so few paragraphs directly violates so many basic, universal human rights,” said High Commissioner for Human Rights Navi Pillay on Tuesday. “Rights to privacy and non-discrimination, rights to freedom of expression, association and assembly, rights to freedom from arbitrary arrest and detention: this law undermines all of them.”

Mrs Pillay warned that the law also risks reinforcing existing prejudices towards members of the LGBT community, and may provoke an upsurge in violence and discrimination. She expressed hope that the Supreme Court of Nigeria would review the constitutionality of the new law as soon as possible.

The law could also undermine efforts against Nigeria’s HIV epidemic. According to the Joint United Nations Programme on HIV and AIDS, Nigeria has the second largest HIV epidemic globally – in 2012, there were an estimated 3.4 million people living with HIV in Nigeria.

“The provisions of the new law in Nigeria could lead to increased homophobia, discrimination, denial of HIV services and violence based on real or perceived sexual orientation and gender identity,” noted UNAIDS Executive Director Michel Sidibé. “It could also be used against organisations working to provide HIV prevention and treatment services to LGBT people.”