The United States do not yet have a confirmation of the reports that Ukraine "disabled" vehicles in a Russian military convoy, but warned Moscow against any attempted incursion into Ukraine without the permission and consent of Kyiv, the White House has reported.

"We are working to gather more information regarding reports that Ukraine's security forces disabled vehicles in a Russian military convoy inside Ukraine. We are not currently in a position to confirm these reports," National Security Council Spokesperson Caitlin Hayden said in a statement released on the White House Web site.

She said that the U.S. authorities had warned Moscow against any attempted incursion into Ukraine without the permission and consent of Kyiv.

"We reiterate our concern about repeated Russian and Russian-supported incursions into Ukraine. Russia has no right to send vehicles, persons, or cargo of any kind into Ukraine, under any pretext, without the government of Ukraine's permission," she said.

Hayden said that the escalation in Russian activity designed to destabilize Ukraine in recent weeks was extremely dangerous and provocative.

"It includes supplying separatist fighters with tanks, armored vehicles, artillery, and multiple rocket launchers (MRLs). Russia has also been firing artillery and rockets from Russian territory into Ukraine on a regular basis, and has been moving multiple-rocket launchers (MRLs) and surface-to-air missile systems (SAMs) across the border to fire on Ukrainian positions – including its newest air defense systems, the SA-22, into eastern Ukraine," she said.

Early on August 15, reporters from Britain's Guardian and Telegraph newspapers reported that a column of 23 armored personnel carriers, supported by fuel trucks and other logistics vehicles with official Russian military plates, had crossed the Russian-Ukrainian border near the Izvaryne checkpoint in Luhansk region, passing through a gap in a barbed wire fence that demarcates the border.

"Last night we saw a Russian incursion, a crossing of the Ukrainian border," NATO Secretary General Anders Fogh Rasmussen told reporters after meeting with Denmark's defense minister on Friday.

Ukrainian President Petro Poroshenko said in a telephone conversation with British Prime Minister David Cameron that Ukrainian artillery units had destroyed part of a convoy of heavy military vehicles that crossed the Ukrainian-Russian border early on August 15.

Ukrainian National Security and Defense Council spokesman Andriy Lysenko confirmed that part of the armored convoy that crossed into Ukraine from Russia through the Izvaryne checkpoint had been destroyed.

However, the Russian Defense Ministry categorically denied the reports of armored vehicles crossing the border, as well as their destruction.