Islamic State fighters have seized villages close to the northern city of Aleppo from rival insurgents, a monitoring group said on Friday, despite an intensifying Russian air-and-sea campaign that Moscow says has targeted the militant group.

News of the advance came as the United States announced it was largely abandoning its failed program to train moderate rebels fighting the Islamic State and would instead provide arms and equipment directly to rebel leaders and their units on the battlefield.

The Obama administration is grappling with a dramatic change in the 4-year-old Syrian civil war brought about by Moscow's intervention in support of President Bashar Assad.