(AFP) - The United Nations Security Council met behind closed doors on Friday to discuss the fast-escalating row between South American neighbors Venezuela and Guyana over a disputed oil-rich region.

World leaders called for calm as Venezuela decried joint US-Guyana military exercises as a "provocation" and vowed to push ahead with its "recovery" of the Essequibo region, which both neighbors claim as their own.

Guyana says Venezuela's move on Essequibo, disputed for more than a century, "threatens international peace and security".

Delegates left Friday's meeting -- which took place at Guyana's request -- with roses offered by Ecuador, chair of the Council this month. None made statements to reporters.

Fears of the conflict blowing up have deepened after Venezuelan President Nicolas Maduro's government held a controversial referendum Sunday on the fate of Essequibo.

Two days after the vote, Maduro proposed a bill to create a Venezuelan province in Essequibo and ordered the state oil company to issue licenses for extracting crude in the region.

The region has been administered by Guyana for more than a century and is the subject of border litigation before the International Court of Justice (ICJ) in The Hague.

It makes up about two-thirds of Guyanese territory and is home to 125,000 of the country's 800,000 citizens, but is also claimed by Venezuela.

Controversy has simmered since 2015 when US oil giant ExxonMobil, operating under licenses from Guyana, discovered vast oil reserves in the area.

"Guyana and ExxonMobil will have to sit down with us face-to-face sooner rather than later," Maduro said Friday during a ceremony in front of the Miraflores presidential palace, where he showed a map of Venezuela that included Essequibo as official territory.

Washington provoked an angry response from Caracas on Thursday by announcing via the embassy in Georgetown that it would hold joint "flight operations within Guyana" as part of "routine engagement and operations to enhance security partnership" with its ally.

"This unfortunate provocation by the United States in favor... of ExxonMobil in Guyana is another step in the wrong direction," Venezuelan Defense Minister Vladimir Padrino Lopez said on social media.

In response, Guyanese Vice-President Bharrat Jagdeo said Venezuela "is not going to succeed, now or ever" at taking the region.

"Every single movement that Venezuelans make, particularly in the proximity of our borders, is tracked, every single one of them," he said.

- 'Unwavering support' -

In Brazil, President Luiz Inacio Lula da Silva voiced "growing concern" Thursday about the tensions on his country's northern border.

Lula told a summit of South America's Mercosur bloc: "If there's one thing we don't want here in South America, it's war."

The Brazilian army said Wednesday it was reinforcing its presence in two northern cities.

British Foreign Secretary David Cameron also warned Venezuela not to take "unilateral action" in the dispute. Guyana is an English-speaking former colony of Britain and the Netherlands.

Russia, a close ally of Venezuela's Maduro, added its voice Friday, urging a "peaceful solution."

The 15-member Caribbean Community (Caricom) also called for a "de-escalation of the conflict and appropriate dialogue" as well as the "avoidance of the use or threat of force".

Guyana insists Essequibo's frontier was determined by an arbitration panel in 1899.

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

In Sunday's referendum, Venezuelans were asked whether citizenship should be granted to the English-speaking people of a new "Guyana Esequiba State" and "consequently incorporating said state on the map of Venezuelan territory."

Officials in Caracas said 95 percent of voters supported the measures.

Analysts say the referendum and the rise in nationalist rhetoric is an attempt to distract attention ahead of elections in 2024 when Maduro will seek a new term amid an economic crisis and dwindling oil production at home.

"It was like a kind of trial balloon ahead of the presidential elections" to measure the "capacity to mobilize and try to fine-tune their strategy for 2024," said Mariano de Alba, an advisor to the International Crisis Group.

© Agence France-Presse