Niger delta rebels had warned that bombs had been planted at the venue of Friday's anniversary parade [AFP]

At least eight people have been killed and another three wounded after two car bombs exploded in Nigeria's capital, Abuja, as the country marks its 50th independence anniversary.

The explosives detonated on the parade grounds surrounding Eagle Square, where celebrations were under way on Friday.

A third, smaller explosion also hit closer to Eagle Square, where the president stood with other dignitaries, injuring one person.

"My information is that there was an explosion in a house," Emmanuel Ojukwu, a police spokesman, told the news agency AFP. "I cannot confirm any fatalities."

Al Jazeera's Yvonne Ndege, reporting from Abuja, said there were indications that police may have been aware of a potential attack.

"Just yesterday the home of the alleged leader of the Movement for the Emancipation of the Niger Delta [Mend], who lives in South Africa, in Johannesburg, was raided by Interpol," she said.

"He spoke to us yesterday, saying that the Nigerian government had informed South African police that he was planning a terror plot, a bomb plot in Abuja. Now it seems that has happened but we don't know whether he's involved in this."

Ndege also added: "There is shock and panic all over Abuja, we are waiting for the inspector general of police to arrive to tell us exactly what they believe to be the cause of this bombing and what they intend to do about it.

"The celebrations seemed to continue as the body bags were being removed from where the car bombs exploded," she said.

Bomb threat

Earlier on Friday rebels from the oil-producing south threatened to bomb celebrations in the city. In an email, fighters from the Niger delta said bombs had been planted at the venue of Friday's lavish parade attended by senior officials and foreign dignitaries.

"Several explosive devices have been successfully planted in and around the venue by our operatives working inside the government security services," the email, signed by Jomo Gbomo, said.

The message urged people to evacuate by 09:30 GMT.

"In evacuating the area, keep a safe distance from vehicles and trash bins."

However, television footage of the parade at the time the deadline expired showed no reaction by security forces.

Ayo Johnson, an African specialist, spoke to Al Jazeera and said that the attackers seem to have backing from inside the security forces.

"The act shows that the security forces on the ground have not been effective because they could have protected the area better.

"This also shows that the perpetrators are getting backing, because they were able to get through the security forces with the president and all the dignitaries there.

"It is a rather embarrassing concern for the government," he said.

Goodluck Jonathan, the president, attended the parade, dressed in his traditional black fedora hat and dark suit, before inspecting massed ranks of soldiers on the rain-swept parade ground from an open-top jeep.

He is from the Niger delta area and analysts have expressed the view that rebels from the same region would not want to cause him serious embarrassment.

Mend has battled the central government for years in a bid to obtain a greater share of federal oil revenues for the impoverished Niger delta.

Source: Al Jazeera and agencies