Tanzania's police force said it was investigating reports that a former ambassador turned government critic had been kidnapped after his family said he was forcefully taken from his house. 

Several critics of the government of President Samia Suluhu Hassan, who will stand for re-election on October 29, have disappeared since last year, with opposition parties alleging a campaign of abductions. 

Humphrey Polepole, who resigned as ambassador to Cuba in July and has repeatedly and harshly criticised Tanzania's ruling party in the months since, went missing from his home in the commercial capital Dar es Salaam early on Monday, his brother, Godfrey Polepole, told Reuters.

"The main door entering the house was broken and the door to the bedroom was broken as well," he said. "There was a lot of blood from the sitting room all the way to the bedroom and the bloodstains continued even outside toward the gate area."

Hassan, who won plaudits after coming to power in 2021 for easing repression of political opponents that was rampant under her predecessor, ordered an investigation last year into reports of abductions, but no official findings have been made public.

Government spokesperson Gerson Msigwa did not immediately respond to a phone call or text message seeking comment. 

In a statement on September 29, the government rejected allegations by Human Rights Watch that it was cracking down on its critics ahead of the election and called accounts of abductions "a major source of concern for the government".

David Misime, a police spokesperson, said the force was investigating reports of Polepole's abduction.   

"The Police Force has seen the reports being circulated on social media by his relatives that he has been kidnapped. We have already begun working ... to ascertain the truth," he said in a statement late on Monday.

After resigning as ambassador, Polepole launched a series of broadsides during online press briefings against the ruling Chama Cha Mapinduzi (CCM), accusing it of flouting party rules by choosing Hassan as its presidential candidate, engaging in corruption and abducting government critics.

Hassan's government has also faced human rights scrutiny over the arrest in April of Tanzania's main opposition leader, Tundu Lissu.

Lissu went on trial on Monday for treason over what prosecutors said was a speech calling on the public to rebel. He has pleaded not guilty and said the charges are politically motivated.