ABOARD AIR FORCE ONE (Reuters) - The United States is "deeply concerned" about the arrests of opposition Kurdish leaders in a terrorism probe in Turkey, a White House spokesman said on Friday.

"This comes on the heels of what appears to be an increase in official pressure on opposition media outlets in Turkey," spokesman Josh Earnest said. "Our deep concerns have already been expressed by senior U.S. officials to their Turkish counterparts," he said. Two co-leaders of the Peoples' Democratic Party (HDP) were arrested on Friday, officials said.

(Reporting by Roberta Rampton, Writing by Timothy Gardner; Editing by Steve Orlofsky)