Tanzanian opposition party Chadema, said two of its members were killed on the eve of Wednesday's local elections, and accused the authorities of rigging the vote.
Chadema said in a statement that a candidate, George Juma Mohamed, was shot dead by police after being attacked by ruling party supporters at his home in Mkese in central Tanzania late Tuesday.
Police confirmed the death and said it occurred after a group of prison officers were called in to deal with a clash between supporters of Chadema and the ruling Chama Cha Mapinduzi (CCM) party.
The prison officers came under attack and fired "warning shots" that led to Juma Mohamed's death, the police said in a statement.
Chadema said another local party leader, Steven Chalamila, was killed in a machete attack in Tunduma near the border with Zambia.
"We condemn the murders that have occurred and demand that the police take immediate action to arrest and bring all perpetrators to justice," the party said.
Chadema also claimed there had been election irregularities in seven constituencies.
It said its agents had found pre-marked ballots for ruling CCM party candidates in several locations, but were arrested by police when they tried to intervene.
"We demand that TAMISEMI (the local government ministry) provide an explanation to the public regarding the pre-marked ballots for CCM candidates in various parts of the country," Chadema said.
Polling stations were due to close at 1400 GMT.
About 31 million Tanzanians are eligible to cast ballots for more than 80,000 street and village leaders who wield considerable power in the East African nation.
Hundreds of voters queued across the country well before the official polls opened.
The ruling Chama Cha Mapinduzi (CCM) party of President Samia Suluhu Hassan, a dominant force for decades, is facing a strong challenge from Chadema that boycotted the polls in 2019 citing violence and intimidation.
Chadema has said many of its candidates were unfairly disqualified from this year's vote.
Party leader Freeman Mbowe was briefly arrested last weekend after police broke up a rally using tear gas, according to the party.
Hassan vowed on Tuesday that it would be a fair contest.
It is a key test for the country's democratic institution ahead of the presidential election next October.
"We are electing local leaders who are also important campaigners during the general election," Chadema's director of communication and foreign affairs John Mrema told AFP on Tuesday, calling the contest an "important pillar".
Hassan took office after the sudden death of her authoritarian predecessor John Magufuli in 2021.
She was initially feted for easing restrictions that Magufuli had imposed on the opposition and the media in the country of around 67 million people.
But rights groups and Western governments have criticised what they see as renewed repression ahead of the votes, with arrests of Chadema politicians as well as abductions and murders of opposition figures.
In 2019, the opposition boycott paved the way for a clean sweep of the seats by CCM.
