RANGOON, Burma (AP) _ A Rangoon-to-Mandalay passenger train struck mines planted by guerrillas and overturned, killing 61 people and injuring 112, the state news agency said Thursday.

The train hit the mines near Kywebwe, 150 miles north of Rangoon, late Wednesday, News Agency Burma said. It claimed that rebels planted the mines, but did not say many exploded or if any group had taken responsibility.

Burma's military has been fighting a dozen rebel groups for decades, including communist guerrillas and ethnic minorities seeking autonomy. About a third of the Texas-sized nation in southeast Asia is not fully controlled by the government.

The Rangoon-Mandalay railroad is the key rail link in the country. Mandalay, Burma's second largest city with 600,000 people, is 400 miles north of Rangoon, the capital.

Guerrillas of the Burmese Communist Party used to stage attacks such as Wednesday's on this rail line, but they were driven from the area long ago and have not attacked the Rangoon-Mandalay line in about 15 years.

The closest rebel-controlled area to Kywebwe is that of the Karen National Union. The group is regarded as the strongest of the ethnic rebel organizations. It's approximately 4,000 fighters operate along the rugged Thai-Burmese border.

Over the last two years, the Burmese army has stepped up its attacks against the Karen, storming some of their camps and disrupting their main source of revenue - a lucrative smuggling trade between Burma and Thailand.

Burma became a one-party socialist republic in 1974. The former British colony's politics have been dominated by Gen. U Ne Win, who took power in a 1962 coup.