UK VIPs pulled out ahead of deadly Nigeria parade
UK dignitaries pulled out of Friday's parade marking Nigeria's 50th anniversary, which was targeted by explosions that killed 12 people.
The Queen's representative had been due to attend but did not and ex-PM Gordon Brown cancelled his visit.
The pullouts have raised questions about how much the Nigerian authorities knew of impending attacks.
The Mend militant group, which is active in the Niger Delta, said it carried them out.
Mend, the Movement for the Emancipation of the Niger Delta, which says it is fighting for a fairer distribution of oil revenue, sent a warning shortly before the blasts.
It said that "several explosive devices have been successfully planted in and around the venue by our operatives working inside the government security services".
It added: "There is nothing worth celebrating after 50 years of failure. For 50 years, the people of the Niger Delta have had their land and resources stolen from them."
Mend later accused officials of acting "irresponsibly by ignoring our forewarning".
But on Saturday, President Goodluck Jonathan was quoted by AFP news agency as saying: "It has nothing to do with Mend... These are terrorists."
He did not elaborate on who he believed carried out Friday's bombings.
The two bombs went off about five minutes apart. Police said the bombs appeared timed to do most damage to those who responded to the first blast.
A UK Foreign and Commonwealth Office spokesperson confirmed it had "received indications of a heightened security risk" and took immediate action to update travel advice after the Mend warning on Friday morning.
The Queen's representative, the Duke of Gloucester, had been scheduled to attend the parade but did not do so. His office declined to comment on why he withdrew. Former UK PM Gordon Brown also did not attend.
The FCO spokesperson said: "Security for VIP visitors is always kept under rigorous review. We remain in constant contact with the Nigerian authorities on this."
Foreign Secretary William Hague condemned the attacks as "cowardly and contemptible".
"My thoughts are with those injured and the families of those who have lost their lives," he said.
Nigeria's This Day newspaper said British intelligence had warned Nigerian authorities of possible attacks.
This Day also reported a raid was carried out on the home of Mend leader, Henry Okah, in South Africa, following Nigerian requests.
Reuters news agency quoted a South African police spokeswoman as saying she could "neither confirm or deny the incident took place".
Nigerian police spokesman Jimoh Moshoo confirmed that 12 people had been killed in the attacks, with 17 injured, and that a manhunt had been launched.
"We have mounted a check throughout the city," he said.
Nigerian President Goodluck Jonathan called the attacks a "wicked act of desperation".
Ordinary Nigerians expressed surprise at the blasts.
Elkana Habila told Reuters: "This is a very massive blow to the Nigerian government... and it will portray the country in a very bad light. It will scare away foreign investors."
Last year the Nigerian government signed an amnesty agreement with rebels in the Delta, offering cash and the promise of job training for former militants who disarmed.
Violence has lessened and the number of kidnappings has fallen since the deal was reached, but many fighters complain the government has failed to deliver its end of the agreement.
Oil production has increased since the amnesty came into effect - from about 1.6 million barrels per day to about two million now.
Most of Mend's attacks have targeted pipelines and supply terminals in the south.
President Jonathan is himself from the Delta region. When he took office earlier this year, a senior rebel leader told the BBC he would be the best person to solve the crisis in the Delta, as he understands its problems.