The United States has imposed sanctions on the commander of Cambodian Prime Minister Hun Sen's bodyguard unit for alleged human rights abuses, the first member of the leader's inner circle to be blacklisted by Washington.

General Hing Bun Hieng, head of the Prime Minister Bodyguard Unit (PMBU), was sanctioned for "being the leader of an entity involved in serious human rights abuse," the U.S. Treasury Department said Tuesday.

The sanctioning of a Hun Sen loyalist comes amid increasingly strained relations between Washington and Phnom Penh. In March, Hun Sen accused the United States of lying when Washington blamed Cambodia's military and other entities for recent political instability and suspended their aid.