BEIJING - Chinese vessels have covered 646,000 square kilometers in the southern Indian Ocean in search of the missing Malaysian flight MH370, said the China Maritime Search and Rescue Center on Tuesday.

Search efforts were about 18,000 square kilometers more than the previous day, said the center.

The center has also mobilized 65 merchant ships for assistance, which have covered 176,000 square kilometers.

No objects related to MH370 have been found, it said.

The international hunt for the plane has been ongoing since the Boeing 777-200 aircraft carrying 227 passengers, including 154 Chinese, and 12 crew members disappeared on March 8 while flying from Kuala Lumpur to Beijing.