The youngsters had responded to a call to join the army in the central African nation, and had been directed to sign up at Brazzaville's Michel d'Ornano stadium.

On Monday night, thousands of youths were in the stadium when a crush occurred as people pushed to get through a gate, security officials said, declining to be named.

Prime Minister Anatole Collinet Makosso said 37 people had been killed in the "tragedy," and an unspecified number injured.

"A crisis unit has been set up under the authority of the prime minister," a statement added.

A 24-year-old, who declined to be named, described to AFP how people were pushing to get through the gate, sparking a stampede.

"There were people injured far worse than me," said the survivor, who dislocated his foot.

Another survivor, who also requested anonymity, said: "There was a row of people in front of me. The people there fell. I fell on top of them and other friends fell on top of us."

Several videos on social media appeared to show dozens of lifeless bodies deposited in a city morgue.

Others showed injured people being admitted to hospitals in Brazzaville.

Morgue official Adelard Yvon Bonda said 32 bodies had been identified by family members.

"We must first of all pay our respects to the memory of those who have just left us," he said.

"This is a situation that arose. It was not provoked, but it happened because young people need jobs," Bonda added.

Tresor Nzila, the head of local rights NGO, called for a full investigation and to hold the Congolese government responsible for not evaluating the risks of a call-up.

"The Congolese government is incapable of creating other employment opportunities," he said. "The defence and security forces have become the main job providers".

The Republic of Congo, which is also known as Congo-Brazzaville to distinguish it from its larger neighbour the Democratic Republic of Congo, is an impoverished country of about five million people -- despite its rich oil and gas reserves.

Youth unemployment in the country is about 42 percent, according to the World Bank.

Congo-Brazzaville's state prosecutor Andre Ngakala Oko said he had launched an investigation.

Congo is no stranger to stampedes. Seven people died in a stampede at a music festival in Brazzaville in 2011.

And at least 150 people were trampled to death in the capital in 1994 when worshippers crammed into a church to avoid a storm.