An activist detained in Tanzania for three days has been released shortly after Kenya’s foreign ministry demanded his release.

A top official in the ministry, Korir Sing’oei, said on X that Boniface Mwangi was “now back in the country”.

Lawyer and fellow activist, Khalid Hussein, told the BBC they were together in Kenya’s coast region.

The Kenyan activist was arrested in Dar es Salaam on Monday alongside Ugandan Agather Atuhaire by suspected military officers and their whereabouts remained unknown.

They had been in the country to attend the court case of opposition leader Tundu Lissu, who is accused of treason.

The Tanzanian authorities have not commented on Mwangi’s detention and deportation.

But on Monday, President Samia Suluhu Hassan warned that she would not allow activists from neighbouring countries to “meddle” in her country’s affairs and cause “chaos”.

Earlier on Thursday, Kenya’s foreign affairs ministry issued a statement saying it had not been able to access the activist.

It said that despite repeated requests, it had been “denied consular access” or information about him, and expressed concern about his health.

It urged Tanzania to “expeditiously and without delay” allow access, or release him, “in accordance with international legal obligations and diplomatic norms”.

Later, Kenya’s state-funded rights commission said it had received the activist in Kwale county, following his release from Tanzania.

KNCHR posted a picture of him alongside other people including his wife, Njeri, and fellow activist Hussein and said he was “in high spirits”. The commission said it was planning to transfer him to the capital Nairobi for medical attention.

The activist was reportedly left at the Kenyan border on Thursday morning following his release by the Tanzanian authorities.

On Wednesday, his wife told the BBC that she had last heard from him on Monday and had not been able to establish where he was.

“I’m actually concerned for his life. I know my husband, he would have communicated, he’d find a way to call or text me and because he hasn’t, makes me very worried about what state he is in,” she told the BBC Newsday radio programme.

Kenya’s foreign ministry on Thursday expressed similar concerns about the activist’s “health, overall well-being and the absence of information regarding his detention”.

It said diplomats should have access to their nationals detained by a host nation in accordance with the Vienna Convention on consular relations.

“In light of the above, the [ministry] respectfully urges the Government of the United Republic of Tanzania to expeditiously and without delay facilitate consular access to or release Mr Mwangi,” it said.

Its statement came amid growing outrage, especially after Tanzania’s deportation of former Kenyan justice minister Martha Karua and other activists, who had also gone to attend Lissu’s hearing, over the weekend.

In recent months, rights groups have been expressing concern at the apparent crackdown on Tanzania’s opposition ahead of elections in October.

Additional reporting by Laillah Mohamed in Nairobi