Washington (CNN) Two US B-52 bombers flew near contested islands in the South China Sea Tuesday, according to a statement from Pacific Air Forces.

The two B-52H Stratofortress bombers, which are based in Guam, "participated in a routine training mission in the vicinity of the South China Sea," the statement said, adding that the flight was part of US Indo-Pacific Command's "Continuous Bomber Presence operations" which have been ongoing since March 2004.

The Pentagon would not confirm which islands the B-52s flew by, but recent tensions have focused on the Spratly Islands.

The US regularly flies aircraft in the South China Sea, but Beijing is particularly sensitive about the operations when they come near areas where the Chinese government has built islands and established military facilities on disputed maritime features.

Pacific Air Forces said Tuesday's "mission is consistent with international law and United States' long-standing commitment to a free and open Indo-Pacific."