A narrow-gauge train overturned Wednesday in a mountainous region in southern Taiwan, killing at least six Chinese tourists, the island's president said.

The Government Information Office said the accident injured 61 other people, 23 seriously. There was no information on their nationalities.

President Ma Ying-jeou said the accident occurred after a large tree collapsed into the path of the oncoming train.

"I feel very grieved by the accident," he said, adding that a thorough investigation would be carried out.

TV footage from the scene showed at least three red and black colored carriages overturned along a hilly gradient, and rescue workers tending to victims.

Taiwan's Defense Ministry said it sent four helicopters to the scene, and rescue services sent three others.

The Alishan rail line, running east from the southern city of Chiayi, corkscrews through a series of steep mountains and has long been one of Taiwan's premier tourist attractions. Most of the line has been closed since a devastating typhoon struck Taiwan in August 2009, but a small portion near the top has since been reopened. It is there the accident occurred.

Alishan has long been a magnet for Chinese tourists.

Ma has made improving relations with China the centerpiece of his three-year-old administration. The two sides split amid civil war in 1949 and the mainland still claims the island as part of its territory.

Under Ma's leadership, commercial ties across the 160-kilometre-wide Taiwan Strait have grown progressively more robust, and tensions between Taipei and Beijing have subsided to their lowest level in 60 years.

One of the most tangible areas of improvement has been a steady rise in the number of Chinese tourists visiting Taiwan. Arrivals in 2010 totaled 1.2 million, enriching the island's coffers by some $2 billion.

The lucrative tourist returns underscore the importance of handling the aftermath of the train mishap with efficiency and tact, to preclude the possibility of a reprise in tensions between the sides.

Late last year Taiwan acted quickly to salve the feelings of the relatives of 20 Chinese tourists killed when their bus skidded off the road during a storm in eastern Taiwan.