Venezuelan coast guard vessels entered Guyana’s waters near Exxon Mobil Corp.’s offshore drilling site over the weekend and transmitted a radio message claiming it was patrolling a “disputed international” maritime zone.

The Venezuelan patrol ship that entered Guyana’s waters Saturday and positioned itself near a vessel contracted by Exxon Mobil Corp. in the Stabroek oil block has departed the area, according to the Guyana Defence Force.

The South American neighbours are involved in a long-running dispute about which country owns the oil-rich Essequibo area.

Guyanese President Irfaan Ali said on Saturday that a Venezuelan coast guard patrol entered Guyanese waters earlier in the day, approaching an output vessel in an offshore oil block managed by Exxon Mobil .

General, the Rt Hon Patricia Scotland KC, has echoed the alarm of Dr Irfaan Ali, the President of the Co-operative Republic of Guyana, after a coast guard vessel from the Bolivarian Republic of Venezuela entered the waters of Guyana on 1.

Guyana and Venezuela clashed again after the former complained of incursion into its oil-rich maritime territory, which then triggered a warning from Caracas against “dangerous provocation” based on “lies”.

Guyana and Venezuela have seen heightened tensions over control of the disputed Essequibo territory, a sprawling region rich in natural resources

Guyana’s government said Saturday that a Venezuelan naval patrol ship entered its waters and approached a vessel contracted by Exxon Mobil (NYSE:XOM) in the Straboek block, according to media reports.