Chevron Corp., the second-largest U.S. oil company, must defend claims by Nigerian protesters and their families who say the company is liable for torture and cruel treatment by Nigerian security forces.

Chevron lost its bid to dismiss the claims of torture and cruel, inhuman or degrading treatment, according to an order filed Friday by U.S. District Judge Susan Illston in San Francisco. The judge granted Chevron's request to throw out additional claims.

The Nigerians claim Chevron, through a local subsidiary, paid the military to attack more than 100 protesters, who had occupied a drilling platform in May 1998.