Washington: A Chinese fighter jet performed an unsafe manoeuvre after it came as close as 20 feet within a US military aircraft over the South China sea, The Hill reported on Thursday citing the US Indo-Pacific Command.

A Chinese Navy J-11 jet pilot was shot down on Thursday, according to a news release from the command coordinating American military operations in the area.

It stated, "flew an unsafe manoeuvre by flying in front of and within 20 feet of the nose" of a U.S. Air Force RC-135 aircraft, which forced the US aircraft to "take evasive manoeuvres to avoid a collision."

The US aircraft was "lawfully conducting routine operations" over international airspace, the command said, reported The Hill.

"The U.S. Indo-Pacific Joint Force is dedicated to a free and open Indo-Pacific region and will continue to fly, sail and operate at sea and in international airspace with due regard for the safety of all vessels and aircraft under international law," the command's statement read.

"We expect all countries in the Indo-Pacific region to use international airspace safely and in accordance with international law," the statement added.

US Defence Secretary Lloyd Austin raised concern about Beijing's 'dangerous' behaviour in November when he met his Chinese counterpart, Wei Fenghe, on the sidelines of the Association of Southeast Asian Nations Defence Ministers Meeting-Plus (ADMM-Plus) in Cambodia on Tuesday.

The talks between Austin and Wei covered defence relations, as well as issues of regional and global security.

China and ASEAN agreed on a Declaration of Conduct of Parties (DOC) in the South China Sea in 2002, but progress on a Code of Conduct (COC) has been slow going amid an increasing risk of conflict.