Seven people were killed and at least 20 others injured in a shooting at the Fort Hood military base in Texas, the US Army confirmed yesterday.

One person has been arrested and at least one more was reportedly on the loose. The base has been locked down.

NBC News network said the two suspects were in military uniform and that the shooter-at-large was believed to have a high-powered sniper rifle.

Fort Hood, located near the town of Killeen, is a large US military base.

Home to about 40,000 US troops, it lies halfway between Austin and Waco, about 60 miles (97 km) from each city.

It is not yet clear whether those reported killed and injured are civilians or military personnel.

Local congressman John Carter, speaking to NBC News, confirmed that there had been a shooting at the base, saying the gunfire had erupted during a graduation ceremony. Schools in the area wer immediately locked down.