A statement from the body's General Secretariat said it noted news from Caracas of "the possibility that aircraft capable of using nuclear weapons from Russia are in its territory" with the "greatest concern."

Russia sent about 100 pilots and other personnel along with two Tupolev-160 bombers and two other aircraft to Caracas -- generating tensions with the US and Colombia, countries Venezuelan President Nicolas Maduro regularly accuses of plotting to assassinate him.

The secretariat branded the mission as "harmful to Venezuelan sovereignty," adding it violated the crisis-hit South American country's constitution because it had not been authorized by its National Assembly.

"Likewise, this action may also be in violation of fundamental norms of international law," it said.

US Secretary of State Mike Pompeo this week condemned the exercises, drawing ire from the Kremlim which branded his response "undiplomatic."