Venezuelan President Nicolas Maduro on Wednesday accused the United States of building "secret military bases" in Essequibo, an oil-rich region of Guyana that Caracas claims as its territory.

"We have information proving that in the territory of Guyana Essequibo, temporarily administered by Guyana, secret military bases of the (US) Southern Command... a body of the CIA, have been installed," Maduro said.

He said the bases are an "aggression" against the people of southern and eastern Venezuela and were built "to prepare for an escalation against Venezuela."

Maduro's provocative remarks came as parliament held a ceremony commemorating a recent law laying out the defense of Guyana Essequibo, four months after a controversial, non-binding referendum overwhelmingly approved the creation of a Venezuelan province in the disputed region, sparking fears of a military conflict.

He also claimed that his counterpart, President Irfaan Ali, "does not govern Guyana" and that "Guyana is governed by the Southern Command, the CIA and ExxonMobil."

Southern Command, part of the Department of Defense, maintains a US Security Cooperation Office in Guyana.

The office serves as a military consultant to the Guyana Defense Force, coordinating "security cooperation engagement activities" and providing military support and training.

The dispute over Essequibo -- which makes up about two-thirds of Guyana's territory and has been administered by Guyana for more than a century -- intensified in 2015 after the discovery of oil deposits by US-based energy giant ExxonMobil.

Tensions soared after December's referendum. Days later, US forces held joint US-Guyana military exercises.

Both countries pledged last year not to use force to settle the border dispute, which is currently before the International Court of Justice in The Hague.