Tanzanian opposition leader Freeman Mbowe is being held at the Central Police Station in the coastal city of Dar es Salaam, his party Chadema says.

Chadema said this came after a search at his house in the city by the police who confiscated his laptop, internet modem and his children’s tablets.

Until Wednesday, Mr Mbowe's whereabouts were unknown following his arrest alongside 11 other members of Chadema in a hotel in Mwanza - in north-west Tanzania, early morning on Wednesday.

The other officials were then taken to the Mwanza Central Police Station.

According to local media in the East African nation, police confirmed the arrest on suspicion of inciting “unauthorised assembly”.

Their arrests came just a few hours before the start of a constitutional conference they were due to hold in the town.

Some human rights organisations have criticised the arrest of the opposition leaders.

Legal and Human Rights Centre and Amnesty International say the arrests are meant to narrow the political space that the opposition is operating in.

Amnesty said the arrests "clearly indicate how Tanzanian authorities disregard the rule of law, human rights, including the rights of freedom and expression".