Civilians flee as security forces aim their weapons at the buildings of a hotel complex in Nairobi, Kenya. Picture: AP Photo/Khalil Senosi

Nairobi - The target of an attack launched Tuesday by suspected al-Shabaab militants on an upmarket hotel complex in the Kenyan capital Nairobi on Tuesday was a conference organised and to be attended by Americans, authorities told dpa.

Terrorist group al-Shabaab claimed responsibility for the assault that began around 3 pm (1200 GMT) with a suicide bombing in the hotel's foyer and an attack on a bank located in the complex, which also features shops and restaurants.

Anti-Terror Police Unit (ATPU) officer Mawira Mungania told dpa that the original target of the attack was a conference at the Dusit Hotel, which is usually frequented by foreigners.

The venue of the conference, however, was changed at the last minute, Mungania said, adding that when the attackers failed to gain access to the hotel they stormed the adjacent building instead.

Kenyan authorities said early Wednesday that "all buildings and surrounding area" were secured after the gunmen holed up for hours in the building in a stand-off with police. They did not name the assailants or said how many took part.

Local media gave conflicting reports as to the number of dead. The Daily Nation said six were killed while The Star newspaper said "several" people were shot dead. There was no official tally.

Early Wednesday the Kenyan Interior Ministry said the "mopping up process still underway."

However, around the same time a dpa reporter on the ground heard the sound of heavy gunfire and two loud explosions from the area. He also reported seeing a large number of people escorted out of the building and nine ambulances leaving the scene.

Authorities subsequently confirmed to dpa that all those hiding in the building had been rescued.

The incident was characterised as a "suspected terror attack" by police chief Joseph Boinnet, who said people had suffered "severe injuries."

Television footage on Tuesday showed people fleeing the complex in panic as smoke poured from the buildings and wounded people were carried out on stretchers. Hospitals appealed for blood donations.

Al-Shabaab, an Islamist group which regularly launches attacks in Somalia and neighbouring Kenya, claimed responsibility on its Radio Andalus.

"Our brave Mujaahideens are engaging in ongoing fighting inside Nairobi against the infidels... The attack started with a bombing," they said.

The United States embassy in Kenya issued a security alert for its citizens, advising them to stay away from the area.

The Kenyan capital experienced one of its worst terrorist incidents in 2013 when at least 67 people were killed in an attack on the Westgate Mall claimed by al-Shabaab.

The al-Qaeda-linked militant group is fighting to topple the country's government and establish an Islamist state based on its strict interpretation of Islamic law.

Al-Shabaab also often targets hotels popular with diplomats, foreigners and senior officials in Somalia, as well as government offices.

The attack at the Dusit comes on the third anniversary of an attack on a Kenyan military base in which almost 200 soldiers were killed.

dpa