Martha Karua, a presidential candidate who also represents opposition figures on trial in neighbouring countries, was arrested in Tanzania on Sunday, a spokesperson told AFP.

Karua said on X network later Sunday that she was "awaiting deportation after retrieving our bags."

Karua has been representing Tanzanian opposition leader Tindu Lissu, who is on trial for treason and faces a possible death penalty.

Lissu is due in court on Monday.

'Democratic backsliding'

The trial comes as Tanzania prepares for elections in October.

Karua "was detained at the Julius Nyerere International Airport in Dar es Salaam, questioned for three hours, her passport was confiscated and she is awaiting deportation", the spokesperson said.

A former justice minister in Kenya, Karua has been vocal about "democratic backsliding" in the East Africa region.

She has also been representing Ugandan opposition leader Kizza Besigye, who was kidnapped in Kenya last year and taken back to his home country to also face treason charges.

'Collaborating in democratic erosion'

Uganda holds elections in January.

"What we are seeing is total erosion of democratic principles in the three countries: Kenya, Tanzania and Uganda," Karua told AFP in an interview earlier this month.

"All these countries now have become dangerous, not just to others but to their own nationals. I tie this to the forthcoming elections," she said.

She accused the leadership of the three countries of "collaborating."

'Neutering the opposition'

"It's a pattern," she said. "They are neutering the opposition ahead of elections."

Karua launched the People's Liberation Party in February, vowing to engage with youths as she prepares a run for the presidency in 2027.

She faces competition from an array of opposition leaders in the country, all hoping to take on President William Ruto, whose popularity was undermined by mass protests last year over tax rises and corruption.

In the 2022 election, Karua was the running mate of Raila Odinga, who lost out to Ruto.

'In total disarray'

Kenya is in "total disarray," she told AFP in the interview this month.

"It's as if our constitution has been suspended. We have abductions, arbitrary arrests... extrajudicial killings... And the police and authorities fail to take responsibility," she said.

Rights groups say at least 60 Kenyans were killed during the protests in June and July, and more than 80 abducted by security forces since then, with dozens still missing.

Police deny involvement.

Tanzania's main opposition party disqualified from upcoming elections

Last week, Ruto told reporters that all those abducted in the wake of anti-government protests "have been brought back to their families... and I have given clarity and firm instructions that nothing of that kind of nature will happen again."

Meanwhile in Tanzania, Lissu's party Chadema was disqualified from the upcoming elections after it refused to sign an electoral code of conduct.

It had demanded electoral reforms, accusing President Samia Suluhu Hassan of returning to the repressive tactics of the country's recent past.

And last week in Uganda, army chief Muhoozi Kainerugaba, who is also son and heir-apparent to the long-ruling President Yoweri Museveni, threatened voters who did not back their party.

Uganda deportation threats

"(People) who do not support Mzee wholeheartedly better be very careful!" Kainerugaba wrote on X, using an honorific for his father.

"We will deport all the traitors in public view!" he added.