CARACAS, Venezuela (AP) — The government of Venezuela accused neighboring Guayana Sunday of granting illegal oil exploration concessions in territory the two nations are disputing. Venezuela said it would reserve the right to take any diplomatic actions necessary.

The comments Sunday came after Guyana said Saturday that it has satellite imagery showing Venezuelan military movements near the South American country’s eastern border with Guyana.

Venezuela's statement did not deny Guyana's claim of a military and infrastructure buildup. Rather, it said it was within its rights to beef up its border forces.

Venezuela claimed Guayana had granted “illegal oil concessions ... in a maritime area that is indisputably Venezuelan.”

Oil giant ExxonMobil has said it will keep ramping up production in offshore fields off Guyana despite the escalation of the territorial dispute.

The two sides have feuded over border lines for decades. Venezuela has been laying claim to the mineral-rich Essequibo region, which covers about two thirds of Guyana’s surface area.

Both sides accused the other of breaching a peace agreement signed in the Caribbean in December to ease tensions over border demarcation lines.

Under the Argyle Agreement signed on the island of St. Vincent in December, the two countries agreed not to use force or to threaten each other. The talks were brokered by Brazil and Caribbean governments.

The latest developments came hours after satellite images posted by the US Center for Strategic and International Studies (CSIS) showed Venezuela is extending its base on Ankoko Island, half of which Venezuela seized from Guyana in the mid-1960s, and nearby Punta Barima, less than 50 miles (80 kilometers) from the Guyana border.

The images showed significant infrastructure improvement of roads and other facilities near the two areas, the CSIS said. Foreign Secretary Robert Persaud noted that “Guyana will continue to respect the Argyle Declaration and hopes that Venezuela will do the same.”

Guyana argues that an 1899 international boundary commission settled the border demarcation once and for all.

But for more than 60 years Venezuela has accused the commission of cheating it out of the Essequibo region.

Guyana has taken the issue to the World Court in the Netherlands for a definitive ruling, while Venezuela has said it prefers direct bilateral talks as the way forward.

On Friday, the Venezuelan defense ministry accused Guyana of threatening the St. Vincent agreement by irresponsible actions and media deception, maintaining that the “Essequibo is ours.”

It also said that ExxonMobil, which is producing 645,000 barrels of offshore oil daily from Guyana, is collaborating with the government and the US military to exploit oil and gas resources in waters claimed by Venezuela.

Guyanese President Irfaan Ali is expected to meet his Venezuelan counterpart, Nicolás Maduro in March for a second summit on the border issue.

Several top American administration and military officials have visited Guyana in recent weeks as a show of support.

The U.S. also supplied military overflights monitoring Venezuelan troop and other activities at the height of tensions in December, in the days leading up to a Dec. 3 referendum in Venezuela that had authorized the annexation of the Essequibo.