Four people have been charged over the siege at the Westgate shopping centre in Kenya's capital, Nairobi, in which more than 60 were killed, police say.

The four foreigners have been charged with aiding terrorist groups in Kenya and being in Kenya illegally.

Their nationalities have not been disclosed, but they are said to be ethnic Somalis.

These are the first charges to be brought in relation to the September siege.

The four have been named as Mohammed Ahmed Abdi, Liban Abdullah, Adnan Ibrahim and Hussein Hassan.

"The accused persons carried out a terrorist attack at Westgate Shopping Mall on 21 September by supporting a terrorist group," the charge sheet read.

All four have pleaded not guilty to the charges, which also included obtaining false identification documents.

None of the men is accused of being the gunmen in the centre.