Kenyan authorities have identified four armed men they say formed the bulk of an al-Shabab group which attacked the Westgate shopping centre in Nairobi.

After the release of video footage of the men inside the mall, Major Emmanuel Chirchir on Saturday named them as Abu Baara al-Sudani, Omar Nabhan, Khattab al-Kene and a man known only as "Umayr".

All "were terrorists", he said, adding that they had all been killed by Kenyan forces at the mall.

David Kimaiyo, Kenya's police chief, told the KTN television station on Saturday that they were among up to half a dozen armed men involved in the attack - contradicting earlier police statements that there had been up to 15 fighters.

The Somali armed group, al-Shabab, said it had carried out the Nairobi attack, which began on September 21, lasted 80 hours and killed at least 71 people.

General Chirchir said Sudani, from Sudan, was the leader of the group and had been trained by al-Qaeda. "He is an experienced fighter and sharpshooter," Chirchir said.

Nabhan, a Kenyan of Arab origin, was born in Mombasa and travelled to Somalia with his uncle aged 16.

Kene was a Somali from Mogadishu, and was linked to al-Shabab, Chirchir said. Umayr's other names, nationality and biography were "not yet identified", he added.

Police chief Kimaiyo said that Samantha Lewthwaite, a British woman dubbed the “white widow” by media for her marriage to London bomber Germaine Lindsay, was not involved in the attack.

At the time of the siege, Amina Mohamed, Kenya's foreign minister, said that Lewthwaite was involved.