ISLAMABAD, Pakistan -- Islamic extremists have resumed small-scale incursions into Indian-controlled Kashmir with Pakistan's tacit support, several militant groups said Friday, threatening to raise tensions over the disputed Himalayan region.

The acknowledgment comes one day after the U.S. ambassador to India said infiltration of militants from Pakistan's portion of Kashmir into India had increased over the past two months.

The incursions have for years been a source of conflict between the nuclear-armed neighbors.

A militant belonging to Al-Omar, a small guerrilla group operating in the region, told The Associated Press that dozens of fighters have moved quietly and mostly unhindered across the Line of Control and into the Indian part of the province.

"We do not face many problems despite the presence of Pakistani troops," he said on condition of anonymity. "Now our fighters are present in a sizable number in Kashmir."

India accuses Pakistan of training, funding and arming the militants, whose campaign has killed more than 60,000 since 1989. Pakistan says it gives only moral, diplomatic and political support.