The CEO and president of Costa Cruises, the owner of the cruise liner that ran aground off Italy killing at least six people, said the captain made an "unauthorized" deviation in course.

The president of the Genoa-based company operating the ship Costa Concordia, Pierluigi Foschi, told a press conference at the company headquarters that "a human error cannot be denied".

"The procedures that were adopted did not meet the strict requirements and documented training,"Foschi said, according to the ANSA news agency.

"Costa Cruises will provide legal assistance to captain Schettino, but the company also has a duty to protect its 24,000 employees. And we cannot deny human error,"he added.

Captain Francesco Schettino has been arrested under charges for manslaughter and abandoning ship, although he denied any wrongdoing.

On Monday, the confirmed death toll rose to six people in the tragic accident occurred last Friday night, when the 290-meter-long ship, with more than 4,200 people from over 60 countries on broad, hit a reef and tore a 70-meter crack in its hull.

There are still 16 people missing, and probabilities of finding them alive inside the vessel diminish as time passes by and weather conditions worsen, local reports said.