Tanzania's Prime Minister Kassim Majaliwa has announced that he will not seek re-election in the forthcoming parliamentary elections, effectively preventing him from being re-appointed.

Majaliwa had earlier said that he would defend his legislative seat for a fourth time in October before making the surprise announcement on Wednesday.

The 64-year-old was appointed prime minister in 2015 and was seen as a possible successor of the late President John Magufuli after his death in 2021.

He has continued to hold the position under President Samia Suluhu Hassan, who is seeking to retain the presidency under the ruling Chama Cha Mapinduzi (CCM).

Majaliwa, who has represented the coastal Ruangwa region since 2010, said his decision was guided by God and he had made it "in good faith".

"It is time to give others the opportunity to unite and build on the development foundation we've established," said Majaliwa, without elaborating on his reasons to pull out from the elections.

It comes just a week after Majaliwa said that he would seek another term in parliament.

He also told Ruangwa residents last September that he would run again, with his unexpected withdrawal sparking speculation of a power struggle within the ruling party.

Majaliwa said he would continue serving as a senior CCM official and support Samia's presidential bid.

In Tanzania, the prime minister leads the government business in parliament and is appointed by the president from among the elected MPs.

Seen as a quiet but firm leader, Majaliwa is credited with ensuring a smooth and calm political transition after Magufuli's death.

The former teacher rose to become an influential figure within the CCM party, which has governed Tanzania since 1977. He served as a junior minister under former President Jakaya Kikwete.

His exit follows that of Vice-President Philip Mpango, who in May announced his retirement from politics.

Analysts say the withdrawal of the two senior politicians gives President Samia space to consolidate her control of CCM and craft her second-term leadership line-up.

Political analyst Nicodemus Minde told the BBC that the move might be part of a plan by Samia to ensure balance at the top of her government, if she wins the elections because they are both Muslim in a country with a Christian majority.

"Something must have pushed him to change his mind about running again for the seat. He has served for 10 years as a prime minister, maybe he feels that is enough," said another analyst, Ezekiel Kamwaga.

The country is due to vote in parliamentary and presidential elections, with CCM expected to retain power. The main opposition party, Chadema, has been banned for refusing to sign up to a code of ethics because it wants a series of electoral reforms.

Initially praised for easing the restrictions Magufuli had imposed on the opposition and the media, Samia has been criticised for what rights groups see as renewed repression. She took up power in 2021 after Magufuli's death, becoming the country's first female president.

Senior Chadema politicians have been arrested and several opposition figures abducted and murdered.

On Thursday, the government dismissed reports of a plot to poison detained Chadema leader Tundu Lissu, who is facing treason charges in court.

It followed concerns raised by Chadema about Lissu's safety while in police custody.

But in a statement, government spokesperson Gerson Msigwa said the Tanzanian authorities have "never had any plan to poison any individual in custody, nor does they have any intention of doing so to anyone".

Msigwa warned the government would take action against those involved in publishing and spreading the "false" information.

Samia's government defends the crackdown on opposition as a move to ensure peace in the country.