The lawyers alleged that security forces deployed across protest sites with orders to suppress demonstrations by any means necessary.
The International Criminal Court has been asked to investigate the violent crackdown and severe human rights violations that followed Tanzania's 2025 general elections.
In a document submitted to the ICC in The Hague, lawyers of alleged victims, backed by the World Jurists Association and the Madrid Bar Association, accused the Tanzanian government of post-election massacres carried out across multiple regions of the country.
Last month, Tanzania conducted its general election, which was marred by allegations of fraud, heavy-handed security operations, and a wave of unrest across several regions.
Keep up with the latest headlines on WhatsApp | LinkedIn
The Tanzanian president, Samia Hassan, won the election with almost 98 per cent of the total votes.
Many international election observation missions characterised the result as fraudulent, emphasising that it lacked credibility.
The African Union (AU) and the Southern African Development Community (SADC) observation missions criticised the elections, saying that they failed to meet all democratic standards.
In the months leading up to the election, all major opposition candidates were jailed or excluded from running.
In April, Tundu Lissu, presidential candidate of the main opposition party, Party for Democracy and Progress, was arrested in a public rally, and subsequently charged with treason and offences under the country's cybercrime laws.
According to the document submitted to the ICC, dated 13 November, a vice chairperson of the party, John Heche, was also arrested in October, a few weeks before the election, and subsequently charged with terrorism.
Mr Mbowe was later released and then rearrested in September.
Demonstrations against electoral fraud
During and after the election, as news of electoral fraud began to spread, protests broke out in major cities, including Dar es Salaam, the state capital, Mwanza, and Arusha. Then it quickly spread nationwide.
The demonstrators set fire to government buildings, burned posters of Ms Hassan, and attempted to block roads.
The response of the security forces to the protest was immediate and lethal, according to the document.
The lawyers alleged that security forces deployed across protest sites with orders to suppress demonstrations by any means necessary.
"Security forces opened fire on protesters with live ammunition. Video footage and survivor testimony document police and military officers firing directly into crowds of unarmed civilians," the document read.
The document, obtained by PREMIUM TIMES, also stated that the Tanzanian government implemented an internet shutdown for six days and blocked VPN services.
"Electricity was also restricted to stop citizens from being able to charge their devices and record evidence of abuse.
The shutdown "prevented protesters from organising and coordinating actions via social media. It blocked real-time documentation and dissemination of security force violence.
"It cut off international media access to information from the ground. Most critically, it created an information vacuum within which security forces could commit mass atrocities without contemporaneous documentation," the document read.
Post-election Massacre
Despite the internet shutdown and electricity restrictions, protests contesting the validity of the election result continued after Ms Hassan was declared the winner.
In Dar es Salaam, Tanzania's largest city, security forces carried out a coordinated assault on protest sites beginning early on 30 October and continuing through 1 November, the document stated.
"When protesters gathered in the Kariakoo commercial district, Mwenge, Ubungo, and other neighbourhoods, security forces opened fire without warning.
"Survivors describe volleys of automatic weapons fire directed into crowds of unarmed civilians. People fled into buildings, side streets, and homes, but security forces pursued them," the document stated.
House-to-house searches were also conducted in neighbourhoods identified as opposition strongholds.
The security officials also carried out mass arrests, torture, and detained protesters.
"Multiple deaths were reported, though the internet blackout prevented real-time documentation," the document states.
However, the lawyers alleged that establishing an accurate death toll from the post-election violence has been difficult due to an information blackout caused by the restriction of internet access, intimidation of witnesses, and the disposal of bodies.
Sign up for free AllAfrica Newsletters
Get the latest in African news delivered straight to your inbox
But opposition parties such as CHADEMA and ACT-Wazalendo put the death toll at more than 1,000.
Western diplomatic missions estimate at least 500 deaths, based on intelligence sources and contacts within Tanzania's security and health services.
Meanwhile, the UN said it has only been able to confirm 10 deaths under its strict verification rules. It acknowledged that access restrictions mean the actual number is likely higher.
Meanwhile, the Tanzanian President Hassan backed the action of the security operatives, claiming the protesters intended to overthrow her government.
She claimed young people had been paid to take to the streets following the election.
"These were not protests; it was violence with malicious intentions. What happened was a manufactured event, and those who planned it intended to bring down our government.
"In that situation, the government has a responsibility, and we swear to defend this country and its borders, to protect the safety of citizens and their property. And in that case, the force used is proportional to the event," she said.
