LAGOS (REUTERS) - Lagos was under a round-the-clock curfew enforced by police on Wednesday (Oct 21), the day after witnesses reported soldiers opening fire on civilians in Nigeria's biggest city, in an incident a rights group said may have caused deaths.

The Lagos state governor said 30 people were hurt in the shooting during a demonstration at a toll gate in the Lekki district, a focal point of nearly two weeks of nationwide protests against allegations of systematic police brutality.

The governor said one man had died in hospital from a blow to the head. It was unclear if he was a protester.

As President Muhammadu Buhari appealed for "understanding and calm", Amnesty International said it was investigating "credible but disturbing evidence of excessive use of force occasioning deaths of protesters" at the toll gate.

Four witnesses said soldiers had fired bullets and at least two people had been shot.

Two of the witnesses said the gate's lights were turned before the shooting began. One said he saw soldiers remove bodies.

In a Twitter post, the Nigerian Army said no soldiers were at the scene.

On Wednesday, fires were burning across Lagos and residents of the districts of Ebute Mette, Lagos Island and Okota reported hearing gunfire.

Police - some armed, some wearing body armour and many in plain clothes - set up roadblocks in Lagos, two witnesses said.

Witnesses saw youths trying to get through some checkpoints, and reported protesters gathering in some areas.

A live feed from local broadcaster Arise TV showed armed police speaking to groups of angry locals, and dozens of charred buses on the Lagos mainland.

In South Africa, hundreds of Nigerians carrying placards demanding "a new and better Nigeria" marched to the Nigerian High Commission in Pretoria.

Nigerian authorities imposed the curfew on Lagos on Tuesday after the governor, Mr Babajide Sanwo-Olu, said the protests had turned violent, including the torching of police stations in the city's Orile Iganmu and Ilasamaja districts.

'The buck stops at my table'

Thousands of Nigerians, many driven closer to poverty by economic fallout from a coronavirus pandemic that has infected more 60,000, killed 1,125 and triggered springtime lockdowns, have demonstrated in protests that initially focused on a police unit, the Special Anti-Robbery Squad (SARS).

The unit - which rights groups for years accused of extortion, harassment, torture and murders - was disbanded on Oct 11 but the protests have persisted with calls for law enforcement reforms.

President Buhari said on Wednesday he was committed to providing justice for victims of brutality, and that the police reforms demanded by the demonstrators were gathering pace.

His statement, disseminated by his spokesman, did not refer to the shooting at the toll gate, from where a witness saw smoke rising on Wednesday.

Mr Sanwo-Olu tweeted pictures of a hospital visit to victims of what he referred to as the "unfortunate shooting incident" in Lekki.

He said 25 people were being treated for mild to moderate injuries, two were receiving intensive care and three had been discharged.

"I recognise the buck stops at my table and I will work with the FG (federal government) to get to the root of this unfortunate incident and stabilise all security operations to protect the lives of our residents," said Mr Sanwo-Olu.

In a broadcast, he urged Mr Buhari to intervene in investigating what happened at Lekki.

Witnesses described being shot at by soldiers.

Mr Inyene Akpan, 26, a photographer, said more than 20 soldiers arrived and opened fire.

Witness Akinbosola Ogunsanya said he saw around 10 people being shot, and soldiers removing bodies.

Another witness, Mr Chika Dibia, said soldiers hemmed in people as they shot at them.

A Nigerian army spokesman did not respond to requests for comment.

Nigeria sovereign Eurobonds fell more than 2 cents on the dollar on Wednesday, as one analyst said the anti-SARS protests might trigger a resumption of attacks on the country's oil facilities, potentially hitting its main source of foreign earnings.

"The Niger Delta militants... have reportedly shown support for the (protest) movement. Should the protests escalate, we could see attacks resume on the oil and gas facilities," said Ms Janet Ogunkoya, senior research analyst at Tellimer Research.