Moscow has accused Ukraine of armed incursions into Crimea — a Black Sea peninsula annexed by Russia in 2014 after having been under Ukrainian administration — dramatically increasing tensions between the two countries.

Ukrainian President Petro Poroshenko ordered troops to be on the “highest level of combat readiness” near Crimea and in eastern Ukraine. As of 11 August 2016, he was seeking urgent talks with Russian president Vladimir Putin as well as French and German leaders, U.S. Vice President Joe Biden and European Council president Donald Tusk.

Meanwhile, Russia launched war games in the Black Sea, and Putin summoned his security council amid fears that the hostility further threatens an already-shaky peace process between the two countries.

Poroshenko also refuted claims aired on Russian state television that Ukraine attacked “critically important infrastructure” in Armyansk, a town near the Ukraine border with Crimea.

The ramping up of military tension comes as Ukraine is preparing to celebrate 25 years of independence from the Soviet Union on 24 August 2016, and as the United States is roughly 12 weeks away from a contentious presidential election in which relations with Russia have been an incendiary focal point.

According to the BBC, Russian state television aired what it called a confession by a Ukrainian man named Yevhen Panov, who the Kremlin claims is a Ukrainian intelligence officer who planned and prepared terror attacks in Crimea. English-language Ukrainian media outlets interviewed Panov’s brother, Igor Kotelyanets, who said that Panov was kidnapped, and would never have gone into Crimea of his own accord.

Reuters showed footage of soldiers escorting handcuffed Panov, who had cuts to his face. Russia said that two servicemen were killed in clashes in early August, and that they  have thwarted a spy network and a plan to bomb infrastructure in Crimea. Kiev denies the accusations, and calls them an excuse for Russia’s military aggression.