Twin blasts at a bus station packed with morning commuters on the outskirts of Nigeria's capital killed dozens of people on Monday, in what appeared to be the latest attack by Boko Haram Islamists.

The explosions rocked the Nyanya station roughly five kilometres (three miles) south of Abuja at 6:45 am (0545 GMT) and destroyed some 30 vehicles, mostly large passenger buses, officials and an AFP reporter said.

The head of search and rescue operations at the National Emergency Management Agency (NEMA), Charles Otegbade, said one of the blasts "emanated from a vehicle" within the station but the precise nature of the explosion was not immediately clear.

No group has yet claimed the apparent attack, but suspicion is likely to fall on Boko Haram, an insurgent group blamed for killing thousands across northern and central Nigeria since 2009.

The Islamists have attacked Nigeria's capital in the past, most prominently in a 2011 car bombing at the UN headquarters in the city that killed at least 26 people.

"Dozens of people were killed in the bomb blasts in Nyanya bus park this morning," NEMA spokesman Manzo Ezekiel told AFP, adding that witnesses reported hearing two separate explosions.

- Charred bodies removed -

The explosions left a hole roughly four feet (1.2 metres) deep and scattered personal items as well as human flesh across the compound, an AFP reporter and witnesses said.

"I saw bodies taken away in open trucks," said witness Yakubu Mohammed. "It is difficult to count them because the bodies were burnt and in pieces."

A second witness, Suleiman Aminu, said he believed the initial blast came from a minibus parked near larger commuter vehicles, and that commuters who had queued up to board were the likely target.

Nyanya is a densely populated suburb of Abuja, filled with government and civil society workers who cannot afford the city's exorbitant rents.

Boko Haram violence has cost more than 1,500 lives already this year, but most of the unrest has affected villages in the remote northeast.

The military in May of last year launched a massive offensive to crush the Islamist uprising and has described Boko Haram as being in disarray and on the defensive.

A major attack in the capital, just a few kilometres from the seat of government, will likely cast further doubt on the success of that campaign.

Bus parks have been among Boko Haram's most favoured targets, including multiple, coordinated bombings at a terminal in the northern city of Kano last year that killed more than 40 people.

Rebels based in the southern oil-producing Niger Delta region have also claimed attacks in the capital, notably a car bombing on independence day in 2010.

But most analysts describe that group, the Movement for the Emancipation of the Niger Delta (MEND), as being largely defunct.

The explosion on Monday "affected quite a number of people because it was still early in the morning and there was a lot of traffic," Otegbade told reporters at the scene.

- President to visit scene -

The private Channels television news network showed images of thick black smoke billowing out from the station.

President Goodluck Jonathan was reportedly on his way to the scene to assess the damage.

Jonathan, expected to face a tough re-election battle next February, has faced mounting criticism of the continuing Boko Haram violence.

An escalation of violence in or near Abuja would pile further pressure on the embattled president.

Boko Haram's leader, Abubakar Shekau, has in recent video messages vowed to widen his insurgency outside the group's northeastern stronghold.