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A suicide bombing blamed on radical Islamist militants killed at least two people in the parking lot of the police headquarters in Abuja Thursday, police said, the latest deadly bombing to roil the capital of Africa's most populous nation.

Another blast Thursday in the country's restive northeast killed three children and was also blamed on the radical Muslim sect known locally as Boko Haram.

Abu Zaid, a man claiming to speak for Boko Haram told the BBC's Hausa language service that the group is responsible for the blast that hit the Abuja police headquarters 8:45 p.m. Zaid's voice was not broadcasted on the radio show. He did not specify that it was suicide bomb.

"They have been issuing threat upon threat," said Nigeria's national police spokesman, Olusola Amore, who blamed the rare suicide bombing on the group.

In a leaflet attributed to Boko Haram and distributed to journalists in Maiduguri Wednesday, a man claiming to be a Boko Haram spokesman warned that the group would launch more attacks after being angered by comments from the national police chief. Inspector General of Police Hafiz Ringim said during a visit to the northeastern city of Maiduguri Tuesday that "the days of Boko Haram are numbered." His office is at the police headquarters in Abuja.

The Associated Press could not immediately verify the authenticity of the statement that also warned residents of all northern states, including the district where Abuja is located, to stay indoors to avoid getting caught in the violence.

Boko Haram, whose name in Hausa means "Western education is sacrilege," has campaigned for the implementation of strict Shariah law. The group is responsible for a rash of killings which have targeted security officers, politicians and clerics in Nigeria's restive north over the last year. Most attacks have occurred in the Boko Haram stronghold of Maiduguri, about 540 miles (872 kilometers) from Abuja.

"If it is Boko Haram, it is clearly a new trend," said Nigerian criminologist and security consultant Innocent Chukwuma, who also heads a foundation that works on police reform. "The group had been carrying out guerrilla-type attacks."

"This could be the first real suicide attack in Nigeria's extant memory," he said. "There have been a number of cases that you can describe as near-suicide, but the cases were not concluded by the police."

Other blasts targeted two police stations and a church on June 7 in Maiduguri, and an attacker died in the car that carried one of the explosives. Police, however, said that his death was accidental.

Nigeria has experienced a rise in bomb attacks in public spaces over the last year, but suicide bombings are practically unheard of.

Amore said Thursday's blast killed the suicide bomber and a traffic warden who rode in the car to show the driver where to park. He said the police had recovered the body of the suicide bomber and started an investigation.

Nigerian Red Cross Umar Mairiga said that nine people have been hospitalized. He said at least two people had died, but it was difficult to confirm a final tally of those killed. Five bags of body parts were recovered from the scene of the blast that left bodies dismembered in the headquarters' parking lot, he said.

Police said 33 cars had been damaged beyond repair and 40 more had been partially damaged by the explosion. The police headquarters building was not affected by the blast.

Attacks on the capital in recent months include a bomb that exploded on New Year's Eve in an open-air beer garden and market at an army barracks in the capital, killing at least four and wounding at least 21, police said.

Dual car bombings killed at least 12 people during Nigeria's 50th independence anniversary celebrations in Abuja on Oct. 1. The Movement for the Emancipation of the Niger Delta, the dominant militant group in the Niger delta region, claimed responsibility for the anniversary attacks.

Meanwhile Thursday, Borno state police chief, Mohammed Abubakar, said three children were killed in an explosion that hit a house in the town of Damboa, about 54 miles (87 kilometers) south of Maiduguri.

Abubakar said the children were playing near the house, and another has been hospitalized. Police also blame Boko Haram for the blast.

Boko Haram's attacks had been restricted to Nigeria's northeast until last month when a man claiming to speak for the group told the BBC's Hausa language service that it was responsible for three blasts that hit the northeastern city of Bauchi, the north-central city of Zaria and a town near the capital. Nigeria's National Emergency Agency said the attacks killed 18 people hours after Nigeria's President Goodluck Jonathan was inaugurated into office.

Jonathan told journalists at the U.N. headquarters in New York on June 8 that he was willing to negotiate with Boko Haram members. The governor of Borno state had previously offered the group an amnesty to calm tensions in the state.

"The bombing in Abuja also signals that Boko Haram is unlikely to accept the amnesty offers," said Alex Thurston, a Northwestern University academic on reformist Islam and electoral politics in northern Nigeria. "Boko Haram's harsh rhetoric and continuing attacks mean that it still views itself as being locked in an armed struggle with the state."

In July 2009, sect members attacked local police stations and government buildings throughout northeast Nigeria. The riots brought a crackdown by Nigeria's military and left more than 700 dead. Boko Haram was then thought to be vanquished after its leader was arrested and died in police custody. But now, Maiduguri and surrounding villages again live in fear of the group, whose members have assassinated Muslim and Christian clerics, police and local leaders and engineered a massive prison break.

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Associated Press writer Njadvara Musa in Maiduguri, Nigeria and Yinka Ibukun in Lagos, Nigeria contributed to this report.