Nigeria's main militant group, which claimed responsibility for October car bombings in Abuja, said it was not behind the New Year's Eve blast in the capital.
A bomb on Friday in a busy market area, where people gather to socialise beside an army barracks, killed at least four people and wounded dozens.
There has been no claim of responsibility for the attack and President Goodluck Jonathan has said the perpetrators have not yet been identified.
"The Movement for the Emancipation of the Niger Delta (MEND) denies any involvement in any of the bombings that took place in Abuja, Nigeria on Friday, December 31, 2010," an e-mailed statement from the group's spokesman said on Sunday.
Though MEND said it planted car bombs in Abuja on Oct. 1 that killed at least 10 people, its previous attacks have tended to avoid civilian casualties. The militant group operates from the Niger Delta where it has attacked oil and gas facilities for years.
At the height of unrest the violence shut down a significant proportion of the OPEC member's oil output and cost Africa's most populous nation an estimated $1 billion a month in lost revenues.