The accident occurred late afternoon in the north-western province of Kocaeli, around 60 km from Turkey's largest city Istanbul and not far from the site of another crash last month that killed 39 people.
Television pictures showed police, troops and ambulance workers clambering over crumpled carriages and using power tools to try to free survivors from the wreckage.
At least one injured passenger was carried away on a stretcher. Others sat by the track holding bandages to head wounds.
One of the trains was an express from Ankara to Istanbul and the other was travelling from Istanbul to the town of Adapazari.
Anatolian said 171 passengers and nine staff were on the express train. Numbers on the other train were unclear.
A highway official told Reuters the Istanbul-Adapazari train suffered the worst of the head-on crash, with four of its carriages damaged and one lying on its side. One of the
carriages in the Ankara-Istanbul train was damaged.
Witnesses speaking on Turkish television said there were many casualties in the front carriages of both trains.
NTV television quoted a local hospital as saying it had admitted 19 injured so far.
Three weeks ago a train disaster in
Turkey left 80 people injured
A senior Transport Ministry official said it appeared one of the trains had run through a red light.
Thirty-nine people were killed less than three weeks ago when another Ankara-Istanbul express, inaugurated in early June as a fast new link between the political capital and Turkey's economic hub, crashed in a similar area.
Officials said initial findings of an independent investigation into that crash indicated the train had been going faster than the official speed limit of 80 km per hour.