Hundreds of people have been killed in Tanzania during three days of protests following Wednesday’s general election, the country’s main opposition party has said.

A Chadema party spokesperson told the AFP news agency that “around 700” people had died in clashes with security forces. A nationwide internet shutdown is making it difficult to verify reports of deaths.

The BBC has spoken to a diplomatic source in Tanzania who said there was credible evidence that at least 500 people had died.

Demonstrations have been taking place in major cities with young protesters denouncing the vote as unfair as key opposition figures were barred from running against President Samia Suluhu Hassan.

Protests have continued on Friday in the main city Dar es Salaam – in the neighbourhoods of Salasala, Yombo and Tegeta – as demonstrators defied warnings from the country’s army chief to end the unrest.

“Some people went to the streets on 29 October and committed criminal acts. These are criminals and the criminal acts should be stopped immediately,” Gen Jacob John Mkunda said on state TV on Thursday, adding that the army had “controlled the situation”.

The government has sought to play down the scale of the violence – and the authorities have extended a curfew in a bid to quell the unrest.

It has been difficult for journalists and human rights groups to check the reports of deaths because of the internet shutdown.

Hospitals in the country have been refusing to give out information when asked about causalities.

A source at one referral hospital in Dar es Salaam told the BBC it had been overwhelmed with casualties since Thursday.

The source added that they had heard this was also the case at other public hospitals in the city where morgues were reportedly full.

The UN has called on the East African nation’s security forces to refrain from using unnecessary or disproportionate force.

“We are alarmed by the deaths and injuries that have occurred in the ongoing election-related protests in Tanzania. Reports we have received indicate that at least 10 people were killed,” Reuters quoted the UN human rights spokesperson Seif Magango as saying earlier on Friday.

The BBC understands that ambassadors from several foreign embassies have also engaged the Tanzanian government to urge restraint from security forces in policing the protests.

By late afternoon on Friday, the electoral commission had announced results from about 80 of the country’s 272 regions, according to the state broadcaster TBC.

The BBC understands that international observers have reported an incredibly low turnout during polling on Wednesday.

President Samia is expected to win the vote under the ruling Chama Cha Mapinduzi (CCM) party, which has governed the country since independence in 1961.

Official results are expected on Saturday.

On Tanzania’s semi-autonomous archipelago of Zanzibar – which elects its own government and leader – the CCM’s Hussein Mwinyi, who is the incumbent president, won with nearly 80% of the vote.

The opposition in Zanzibar said there had been “massive fraud”, the AP news agency reported.

Tourists on the island are also reported to be stranded at the airport, with flight delays because of the protests, which have been on the mainland, and the internet shutdown.

A Kenyan music publicist said she was stranded for three days in Tanzania because of the communication problems.

“Internet, shops, petrol stations, email, social media, everything was down. Total disconnect. No international or regional calls in or out. No text messages in or out. There were no Ubers or Bolts available because there was no network,” Anyiko Owoko posted on Instagram after making it home on Friday on a Kenya Airways flight.

“Many flights were cancelled, Tanzania’s national airline was grounded. There were so many people stranded at the airport who couldn’t book tickets or reschedule flights because of the connectivity blackout,” she said.

The protesters accuse the government of undermining democracy, as the main opposition leader, Tundu Lissu, is in jail and another opposition figure was disqualified from the election, bolstering Samia’s chances of winning.

Lissu is being held on treason charges, which he denies, and his party boycotted the vote.

The only other serious contender, Luhaga Mpina of the ACT-Wazalendo party, was excluded on legal technicalities.

Sixteen fringe parties, none of whom have historically had significant public support, were cleared to contest the elections.

Samia came to power in 2021 as Tanzania’s first female president following the death in office of President John Magufuli.

She was initially praised for easing political repression, but the political space has since narrowed, with her government accused of targeting critics through arrests and a wave of abductions.

Additional reporting by Stewart Maclean and Basillioh Rukanga