A train collided with a truck loaded with opposition party activists going to vote Saturday, and at least 16 people were killed and 11 seriously injured, officials said.

The accident took place at El Quebrachal, a small town 150 miles southeast of the provincial capital of Salta. The town's mayor, Pedro Sandez, said the crash occurred when a flatbed truck collided with a train at an unmarked rail crossing.

Thirty people were in the truck, including several children. Most were opposition Peronist Party activists headed to vote in primary elections to choose their party's presidential candidate.

Seven of the injured were taken to a hospital in grave condition in the nearby town of Joaquin V. Gonzalez, officials said.