WASHINGTON (AFP) - A Venezuelan fighter jet "aggressively shadowed" an American intelligence plane over the Caribbean Sea, US defence officials said Sunday (July 21), slamming the manoeuvre as "unprofessional."

US Southern Command (SOUTHCOM) said the Russian-made Venezuelan SU-30 "Flanker" took off from an airfield 200 miles (320 kilometres) east of Caracas on Friday, following a US EP-3 at an "unsafe distance...jeopardising the crew and aircraft."

"The EP-3 aircraft, flying a mission in approved international airspace, was approached in an unprofessional manner by the SU-30... The US routinely conducts multi-nationally recognised and approved detection and monitoring missions in the region to ensure the safety and security of our citizens and those of our partners," it added.

SOUTHCOM said in a separate post on Twitter the action demonstrated Russia's "irresponsible military support" to Venezuelan President Nicolas Maduro's "illegitimate regime."

It also revealed Maduro's "recklessness & irresponsible behaviour, which undermines international rule of law & efforts to counter illicit trafficking," it added.

The South American nation was plunged into political turmoil in January when National Assembly speaker Juan Guaido declared himself acting president in a direct challenge to Maduro's authority.

The opposition leader is recognised by the United States and more than 50 other countries, but has been unable to dislodge Venezuela's socialist leader.

The US has accused Russia of propping up Maduro as the crisis deepened by supplying military aircraft including the SU-30.