Tanzanian President John Magufuli has vowed to allow "free and fair" elections as he seeks a second term in October's general election.
He told politicians to "avoid insults and violence" while campaigning as he announced the dissolution of parliament as required by the constitution.
Supporters of Mr Magufuli have nicknamed him "bulldozer" praising him as a hands-on leader who has helped deal with endemic corruption in government.
His critics, however, say he has stifled freedom of expression since he took office in 2015.
Under his presidency, human rights bodies and journalists have been targeted, some for making fun of him.
Opposition politicians have also accused him of being a dictator. Some of them have been physically assaulted though the attackers' motives have not been established.
Recently Freeman Mbowe, the leader of the main opposition Chadema party, was allegedly beaten and hospitalised in what his party said was a "politically-motivated" attack.
Despite focusing on the general election a cloud of uncertainty hangs over Tanzania because of its handling of the Covid-19 pandemic which Mr Magufuli declared "finished".
The authorities, however, said on Monday that the country has only 66 active cases of Covid-19.
