GEORGETOWN, Guyana (AFP) — Guyana said Thursday its soldiers had come under attack three times in 24 hours in a disputed oil-rich border region where neighbor Venezuela plans to hold elections this month.

Armed men in civilian clothing carried out three separate attacks on troops conducting patrols on the Cuyuni River in the disputed Essequibo region, the Guyana Defence Force (GDF) said.

“On each occasion, the Guyana Defence Force executed a measured response, and no rank sustained any injuries,” it said in a statement, vowing to “continue to respond to acts of aggression along the Guyana-Venezuela border.”

Both countries lay claim to Essequibo, which makes up two-thirds of Guyana’s territory and is home to 125,000 of its 800,000 citizens.

Guyana has administered the region for decades, and insists Essequibo’s frontiers were determined by an arbitration panel in 1899.

The Guyanese foreign ministry said it had condemned the attacks in a diplomatic note to Venezuelan authorities and asked that it launch an investigation “so that the perpetrators are arrested and brought to justice.”

Venezuela claims the Essequibo River to the region’s east forms a natural border recognized as far back as 1777.

The long-running squabble was revived in 2015 after US energy giant ExxonMobil discovered huge crude reserves in Essequibo and reached fever pitch in 2023 when Georgetown started auctioning off oil blocks in the region.

The find gave Guyana, a small English-speaking former British and Dutch colony, the largest crude oil reserves per capita in the world.

Caracas has since held a referendum asserting its claim to the territory, and has threatened to annex most of the region and make it Venezuela’s 24th state.

It has also announced Essequibo will be included in gubernatorial elections planned for May 25, despite the UN’s top court ordering it not to organize a vote there.

The GDF said Thursday it “remains resolute in its mission to protect Guyana’s territorial integrity” and was taking “all necessary measures to safeguard the nation’s borders and maintain peace and security within our beloved country.”

Tensions calmed after the two countries’ presidents agreed in Saint Vincent and the Grenadines last December 2023 to avoid any use of force, but were fanned again in February when Guyana said six of its soldiers were wounded in an ambush in the region.