Human rights groups in Guinea say they believe more than 135 football fans were killed in a crush at a stadium on Sunday, most of them children.

The figure, which is unverified, far exceeds the official number of deaths at 56.

The groups said the estimate was based on information from hospital, cemeteries, witnesses at the stadium, families of victims, mosques, churches and the local media. More than 50 others are still missing, it said.

The military government, however, has warned against spreading "unverified" information, saying that its investigations are ongoing into the tragedy in the country’s second largest city, Nzérékoré.

He said anyone disseminating "unverified or malicious information", would be arrested and prosecuted.

The deadly incident followed a controversial refereeing decision during the match, which led to violence.

Police responded with tear gas, as people tried to flee.

But the rights groups blamed the deaths on the game's organisers and Guinea's ruling military junta, who held the tournament in honour of President Mamady Doumbouya.

The collective of rights groups in Nzérékoré said there was excessive use of tear gas in an enclosed area, adding that vehicles carrying officials leaving the stadium also hit citizens who were trying to escape.

Prime Minister Mamadou Oury Bah on Tuesday announced three days of national mourning for the victims.

Government spokesman Ousmane Gaoual told local Guineenews site that the country was "in mourning and we must respect the mourning of Guinea and the families" in response to a query about the number of victims.

"The government announces provisional figures and someone comes up with other figures, where is the contradiction? We didn't say that these are final figures," he was quoted as saying.

A local journalist in Nzérékoré earlier told the BBC that the stadium had been "packed to the rafters" with thousands of people before the deadly incident.

Paul Sakouvogi said the stadium had "only one exit... which was very small", where the crush occurred as people tried to flee.

Guinea is among several African countries that are currently banned from holding international football matches for not meeting international standards.

Others barred by the Confederation of African Football (Caf) from such matches include Ethiopia, Gambia, Chad and Sierra Leone.