Syria's President Bashar Assad says his government has been receiving general messages from the American military about airstrikes targeting the Islamic State group inside Syria but that there is no direct coordination.

In an interview with the BBC aired Tuesday, Assad says the messages are conveyed through third parties, such as Iraq.

"Sometimes they convey message, general message, but there's nothing tactical," he said.

A U.S.-led coalition is conducting airstrikes in Syria as part of an international campaign against Islamic State extremists. They share the skies with Assad's air force, which also targets the militants.

In the interview, Assad denies his forces have used barrel bombs. The government's use of the crude explosive devices, usually dropped by helicopters, has been widely documented by international human rights organizations.