Rampant looting has been reported in the upmarket Westgate mall in Kenyan capital Nairobi following the four-day al-Shabaab siege, with tenants saying they have suffered huge losses from burglary.

Enraged businessmen at the luxury shopping centre have complained to security forces over the theft of goods worth several million Kenyan Shilling (£1 = 139 KES).

The shops on the first three floors were shut down in the initial stages of the siege. Tenants were shocked to see the shops ransacked when they returned to the plaza days after the militants' attack.

"There is a crisis here because the owners of some of the shops that dealt in valuable goods and who have been allowed inside the building are shocked to find that their premises were looted by unknown people. They are demanding to be told what happened and who took their goods," an unidentified security officer told Kenyan daily The Star.

The premises of Swiss-based luxury watch manufacturer Rado's were reportedly ransacked during the looting, along with several other jewellery shops. Expensive electronic gadgets were also targeted by the looters.

"We wish to affirm that government takes very seriously allegations of looting and that those found to have engaged in looting will be prosecuted," senior government official Joseph Ole Lenku told a press conference.

Three suspected looters have so far been detained by the police. Authorities are probing whether any of the employees or the security forces involved in the anti-terror operation took part in the looting.

Civilians who sought refuge in the banks while the attack was on escaped from the mall with cash, reports have suggested. The Kenyan authorities have not restored the tenants' full access to shops as the investigation is progressing.