(Changes dateline to BOGOTA from WASHINGTON; adds quake felt inland)
BOGOTA, Aug 13 (Reuters) - A strong offshore earthquake of magnitude 6.5 shook several towns in western Colombia on Tuesday, but no damage or injuries were reported, the country's Geological Service said. No tsunami warning was issued.
The quake struck at 10:43 a.m. local time (11:43 a.m. EDT/1543 GMT) at a depth of 21 km (13 miles) and nearly 100 km west of Colombia's Pacific coast.
The U.S. Geological Survey put the intensity of the quake at a higher magnitude of 6.7 and said it happened at a shallower depth of 10 km (six miles).
Residents in several towns in the southwest and in central Colombia said the quake caused strong shaking, the head of the seismic detection network at Colombia's geological service, Jaime Raisgosa, told Reuters.
The Alaska Tsunami Warning Center, which covers this region of the Pacific, said no tsunami warning was issued. (Reporting by Jackie Frank and Luis Jaime Acosta; Writing by Peter Murphy and Jackie Frank; Editing by Philip Barbara and David Brunnstrom)