Tanzania's President Samia Hassan has opened campaigning for elections in October, which comes as key challengers have been locked up or prevented from running.

Hassan came to power without being directly elected after taking over from John Magufuli when he died in March 2021, and she seems not to be taking chances in the run-up to the presidential and parliamentary votes.

The opening campaign event in the economic capital Dar es Salaam was a glitzy affair featuring popular musicians, just as Hassan told supporters her party had accomplished major milestones and has the energy to continue leading the country.

She also promised expanded healthcare and to tackle controversy over hospitals withholding bodies of deceased persons over unpaid bills.

The President also promised to establish a reconciliation commission and start the process of drafting a new constitution, though she gave no details of what these processes would involve.

Authorities in the east African country have increasingly cracked down on the opposition, drawing criticism from international rights groups and Western governments.

In April, the main opposition party, Chadema, was disqualified from the elections after its leader Tundu Lissu refused to take part without major voting reforms.

This week, the electoral commission also disqualified Luhaga Mpina, candidate for the third-largest party, the Alliance for Change and Transparency, saying he lacked "qualifications".

Hassan's candidature has faced some criticism from within her own party, the Party of Revolution (CCM).

Its former ambassador to Cuba, Humphrey Polepole, resigned in July after mounting criticism of political abductions in Tanzania.

At the recent rally, the party's vice-chair Stephen Wasira accused critics of opposing a female president "because of the male-dominated system, just as some supporters of the president are unconcerned by the crackdown on the opposition.

"We have many other parties competing," said Mashaka Ngao, who travelled some 40 kilometres to attend the rally.

We would still have won. There is no party that can compete with CCM," he told reporters.

But another CCM supporter, Omary Mrisho, said it was a shame that Chadema was excluded.

"Chadema usually livens things up. They push our leaders to think of better ideas... They are our rivals but we need them," he said.