The Nigerian authorities have dropped treason and other charges against dozens of protesters, including more than 30 children, who were arrested in August after taking part in anti-government demonstrations.

President Bola Tinubu had already called for the release of all the minors - some as young as 14 - after footage of four of them collapsing in court on Friday, apparently due to malnourishment, sparked outrage.

He also said the police and other officials involved in the arrests and subsequent legal processes should be investigated.

The viral videos of the young people writhing in pain led to a renewed debate over their treatment, as well as the length of their detention.

Initial reports had talked of 27 young people being affected, but details of another set of detainees, including more between the ages of 14 and 17, have emerged since.

The suspects had been in custody for nearly three months after participating in the #EndBadGovernance protests which swept the country in August over a deepening cost-of-living crisis.

The demonstrations turned violent in some places when protesters clashed with security forces.

Police say seven people died - though rights groups put the death toll at 23. Nearly 700 people were arrested.

Some of those in court in the capital, Abuja, on Friday were accused of flying Russian flags and planning to overthrow the Nigerian government.

In a statement on Monday, President Tinubu's spokesman Bayo Onanuga said the Nigerian humanitarian affairs ministry had been asked "to ensure the safe return of all the minors to their families while an investigation has been opened into the circumstances leading to their prolonged detention".

When the courtroom footage emerged, Nigerian rights organisation Enough is Enough said they had been subjected to "institutional child abuse".

Amnesty International described the children's detention was "one of the deadliest attempts to suppress freedom of assembly" so far.

Observers say the move to drop the charges and release the children was a face-saving measure and that the government would have avoided the embarrassment if it had not engaged in a high-handed approach against protesters demanding better governance.