Jimoh Moshoo, police spokesman in the capital, Abuja, said 17 people were wounded in Friday's blasts, which went off about an hour after an emailed bomb threat from a rebel group in the oil-producing Niger Delta.

The Nigerian newspaper This Day, citing presidency sources, said British intelligence has got wind of a plot and passed on a warning to Abuja. Britain's Duke of Gloucester, who was due to represent Queen Elizabeth at the event, pulled out.

The secret service in Africa's most populous country confirmed it had received foreign tip-offs and had stepped up security accordingly, including towing 65 vehicles from the streets and cordoning off roads leading to the parade ground.

"If we had ignored them the situation could have perhaps been worse than what happened," State Security Service spokeswoman Marilyn Ogar said.

News organizations including Reuters received an emailed bomb warning about an hour before the explosions, signed by Jomo Gbomo, principal spokesman for the Movement for the Emancipation of the Niger Delta (MEND).

In a statement on October 2, MEND said it regretted the deaths, adding that it had given the security forces five days' notice.

The group has been fighting for years for a greater share of oil revenues for the delta, home to Africa's biggest oil and gas industry, but signed an amnesty with the government last year.