CARACAS, Venezuela (AFP) — Venezuela traded accusations with Guyana Tuesday over disputed waters off the South American coast where Exxon Mobil recently announced a significant offshore oil find.

The Venezuelan foreign ministry took umbrage at a warning by Guyana on Monday that it would resist any effort by Caracas to enforce a recent decree laying claim to the disputed area.

Venezuela charged that Guyana was trying “to create an artificial crisis, inventing irrational situations against a brother country like Venezuela, and using highly offensive language.”

The decree issued by Caracas on May 27 lays claim to waters off the Essequibo, a disputed territory that borders Venezuela and encompasses more than half of Guyana.

The Venezuelan action came less than a month after Exxon Mobil said it had made a significant discovery in an offshore concession granted by Guyana.

In its statement Monday, Guyana’s foreign ministry said the Venezuelan decree was a violation of international law and a threat to regional peace and security.

“Any attempt by the Bolivarian Republic of Venezuela to apply that instrument in an extra-territorial manner will be vigorously resisted by the Cooperative Republic of Guyana,” the foreign ministry statement said.

The statement stressed that Guyana would continue to access and develop its offshore natural resources.

Venezuela described the decree as “an administrative norm directed at organising the everyday work of maritime supervision and protection”.

Guyana, a former British colony, maintains that the land boundary was settled in 1899 by a court of arbitration set up after a crisis that prompted the United States to intervene in favour of Venezuela against Britain, asserting the Monroe Doctrine.

Venezuela has never recognised the line, and the dispute has simmered ever since, extending in recent years to maritime rights off the disputed area.

In 2013, Venezuela’s navy intercepted a Malaysian-owned oil exploration vessel in an offshore concession that Guyana granted to the Texas, US-based oil company Anadarko Petroleum Corporation.