HONG KONG — A merchant ship collided with a Malaysian oil tanker on Tuesday morning, puncturing the tanker’s hull and spilling 2,500 tons of crude oil into the Singapore Strait, maritime officials reported.

The damage appeared to be limited to one compartment in the double-hulled tanker, the Bunga Kelana 3, with the spill amounting to about 18,000 barrels. In comparison, the most conservative estimates of the ongoing BP spill in the Gulf of Mexico are 5,000 barrels a day.

The spill occurred about seven miles offshore, southeast of the Changi East complex, the home of the Singaporean Air Force.

The Maritime and Port Authority of Singapore said by midafternoon that an oil slick had formed measuring 2.5 miles long and more than a half-mile wide. The agency was coordinating cleanup efforts, which included two oil skimmers, chemical dispersants and a mile of containment booms.