A leading Kenyan activist was arrested at his hotel in Tanzania where he had planned to attend an opposition leader’s treason trial, his wife told AFP on Tuesday.

Boniface Mwangi — one of the most prominent campaigners against corruption and police violence in Kenya — was among several regional activists who travelled to Tanzania to show solidarity with opposition leader Tundu Lissu during his court appearance on Monday.

Lissu’s Chadema party has been banned from taking part in elections due in October after insisting on reforms.

Several activists, including Kenyan presidential candidate Martha Karua, were denied entry at the airport ahead of his latest hearing and deported.

Mwangi’s wife Njeri told AFP she had not been able to contact him since his arrest.

“I have been told they are waiting for the government of Tanzania to consult and decide whether to charge him or to deport him,” she said.

Tanzanian President Samia Suluhu Hassan said Monday that foreign activists would not be allowed to interfere in the country’s affairs and urged security organs “not to allow ill-mannered individuals from other countries to cross the line here”.

According to Njeri, Mwangi was taken from the Serena Hotel alongside Ugandan activist Agather Atuhaire.

They spent the night at the central police station in Dar es Salaam, his lawyer Jebra Kambole confirmed to AFP.

Activists say the events in Tanzania are part of a wider erosion of democracy across east Africa.

In neighbouring Uganda, opposition leader Kizza Besigye is also on trial for treason after being kidnapped in Kenya and taken across the border.

Karua, the Kenyan presidential candidate, is serving as his lawyer.

She travelled to Uganda on Tuesday ahead of Besigye’s latest hearing the following day, and posted online that “entry was without a hitch”.