The trial of four men charged over the Westgate shopping centre siege in Kenya has started in the capital, Nairobi.

They deny charges of aiding a "terrorist group" and being in Kenya illegally.

Somalia's al-Qaeda-linked al-Shabab group carried out the four-day siege in September, killing 67 people.

The four are the first to be charged over the attack - the worst in Kenya since 224 people were killed in the 1998 bombing of the US embassy.

Norwegian suspect

The nationalities of the men have not been disclosed, but they are said to be ethnic Somalis.

The police say the four accused had sheltered the attackers in their homes in Eastleigh - a Somali neighbourhood in Nairobi - and that they were in contact with the gunmen four days before the siege.

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

None of the men is accused of being the gunmen who carried out the attack in the upmarket shopping centre.

The Kenyan army has said that all four of the attackers died during the siege.

One of the suspected attackers has been named as 23-year-old Somalia-born Norwegian national, Hassan Abdi Dhuhulow.

Al-Shabab is fighting for an Islamic state in Somalia.

It said it carried out the attack to avenge the presence of Kenyan troops in Somalia to bolster the UN-back central government.