DAR ES SALAAM: Police in Tanzania have arrested a woman after a video clip showing her kissing and embracing another woman at a party was widely shared online, a senior official said.

Homosexuality is a criminal offence in the East African nation, where a conviction for having "carnal knowledge of any person against the order of nature" can carry a life sentence.

The woman, who police said resides in the northwestern Tanzanian town of Geita, was arrested after a video circulated on social media showing a woman kissing and hugging another woman and presenting her with a ring.

"I can confirm that a Tanzanian woman is under police custody over that video clip. We will issue more details later after we conclude our investigation," Geita police chief Mponjoli Mwabulambo told Reuters by telephone on Saturday.

Tanzanian president John Magufuli's government has stepped up a crackdown against homosexuality since coming into power in 2015 and threatened in June to arrest and expel activists, as well as deregister all non-governmental organisations that campaign for gay rights.

In October, authorities in the main city Dar es Salaam raided a meeting at a hotel, saying the gathering was promoting same-sex relationships, and arrested at least 12 men.

The arrest of the woman in Geita was thought to be the first arrest of a lesbian suspect in the recent crackdown and police sources said authorities were also searching for the woman who was given the ring in the video clip.

Reuters could not confirm where or when the video the filmed.

The clip drew condemnation on social media platforms in the socially conservative nation, with some Tanzanians condemning the celebration as immoral.

"Both of them should be arrested. Why did the woman accept an engagement ring from another woman?" Cosmas Alele, a resident of the northwestern town of Kagera said on Twitter, writing in Kiswahili.

Since homosexuality is a criminal offence in Tanzania, rights groups are reluctant to speak publicly in defence of gay rights.

The country's health ministry banned non governmental organisations last year from distributing free lubricants to gays as part HIV/AIDS control measures.

Some health experts warn that shutting down HIV/AIDS outreach programmes targeting gay people could put the wider population at higher risk of infections.

Around 1.4 million Tanzanians among a population of more than 50 million are living with HIV, the virus that causes AIDS, according to government estimates.