Protesters drove a bus into police lines in the Pacific coast resort of Acapulco, injuring at least seven officers, according to Mexican federal officials.

The Interior Department said that five protesters also were injured in the confrontation Tuesday evening, which came after thousands of protesters had tried to block entrances to the Acapulco airport, prompting police to ferry tourists to the terminal in trucks.

When police tried to open the entrance roads, a protester drove a bus into them. The department said some protesters had been detained, but did not give a precise number.

When the violence broke out, local police said they sheltered some airport-bound tourists at a local police station.

The estimated 4,500 demonstrators belong to two radical unions protesting the Sept. 26 disappearance of 43 students. Those students were detained by police in the city of Iguala in the same state. The city police turned them over to a drug gang, which apparently killed them and incinerated their remains.

The government of the southern state of Guerrero, where Acapulco is located, said state police assisted six people injured in the protest, including a 70-year-old man with a head wound that required hospitalization.

Acapulco is hosting the Mexican Open tennis tournament, which was not interrupted. A small group of protesters arrived outside the site of the tournament earlier Tuesday but were quickly surrounded by police.

Acapulco hotel owners and businesses have complained that months of protests, bus hijackings and highway blockades related to the students' disappearances have hurt Acapulco's once-thriving tourism industry.