WARSAW, SZCZEKOCINY, Poland -  Poland's President Bronislaw Komorowski announced a two-day national mourning period on Sunday for the 16 people killed in a head-on collision of two trains in the country's worst rail accident in more than two decades.

The trains collided at an average speed of 100 km (60 miles) near the town of Szczekociny in southern Poland on Saturday night after one of them switched to the wrong track minutes before the crash, said Transport Minister Slawomir Nowak.

"You can only imagine the horrific toll this caused," he told a news conference.

Most of the carriages had derailed, some were crumpled or broken in half and others were lying on their side along the track. 

Rescuers recovered 16 bodies from the wreckage and were able to identify nine of the victims, Interior Minister Jacek Cichocki said. Nearly 60 of the estimated 350 passangers on board were injured. Three remained in intensive care.

Cichocki said authorities could not rule out finding more bodies as heavy machinery continued to pull apart the heaps of metal.

"The scope of this disaster is sufficiently large to warrant national mourning," said President Bronislaw Komorowski from the site of the accident.

Komorowski also visited some of the survivors in hospital.