Four Chinese sailors were missing after their tugboat hit a ship of the Republic of Korean (ROK) early Monday morning and sank near a harbor in east China's Shanghai Municipality.

The collision took place at 0:39 AM Monday when the Chinese boat, which was towing another ship, and a ROK-registered container carrier "Star Mariner" were approaching the Wusongkou Port.

The tugboat sank after the collision, throwing all the ten sailors into the water.

Rescuers lifted six shipmen out of the water, but the other four remained missing.

Eleven ships went searching for the missing people Monday morning, but heavy fog hampered the rescue operation.

Investigation into the cause of the accident is under way.

(Xinhua News Agency April 10, 2006)