London: The UN's maritime agency may re-examine international safety regulations for large passenger ships in the wake of the Italian liner disaster, the organisation said on Tuesday.

Italian rescuers were desperately searching for at least 15 missing people off the Tuscan coast on Tuesday following the capsizing of the Costa Concordia cruise ship, which has killed at least six people.

"IMO must not take this accident lightly," the International Maritime Organisation's Secretary-General Koji Sekimizu said, expressing condolences to those caught up in the tragedy.

"We should seriously consider the lessons to be learnt and, if necessary, re-examine the regulations on the safety of large passenger ships in the light of the findings of the casualty investigation."