DAR ES SALAAM, April 23, 2025 (BSS/AFP) - Tanzanian police on Tuesday arrested the deputy head of an opposition party whose leader has already been detained, the party said, amid accusations of a clampdown ahead of a presidential election this year.

Chadema party vice-chairman John Heche, a national assembly member, was detained at a rally on Tuesday in the East African state's economic capital Dar es Salaam, the party said.

Chadema leader Tundu Lissu and other party members were arrested this month. He is to appear in court on Thursday on treason charges that carry a possible death sentence.

Heche had called for a demonstration to support Lissu, despite police warnings.

Police called for Tuesday's protest to be moved, but Chadema said the police notification only arrived at the last minute.

Chadema spokesperson Brenda Rupia said the party had been unable to find out which police station Heche had been taken to.

"We believe these arrests are part of a calculated strategy to paralyze the opposition's constitutional mandate, suppress the voice of the people, and restrict political space as the country prepares for a crucial election period," Chadema said in a statement.

A government official recently said Chadema would be excluded from looming elections because it had refused to sign a code of electoral conduct. Chadema has demanded reforms in the code.

Lissu and Heche have accused President Samia Suluhu Hassan of resorting to authoritarian tactics. Rights groups and some western governments have also criticised events, including the arrests and deaths of some opposition activists.