KIEV, Ukraine — The government of Ukraine, pushing to oust pro-Russian rebels from their last enclaves in the east while nervously eyeing a stalled Russian aid convoy, said on Friday that its force had destroyed a number of Russian military vehicles that it said crossed into Ukraine late Thursday through a border area controlled by the separatists.

Russia denied sending a military column into Ukraine, but the incursion, first reported by British journalists who said they saw 23 armored vehicles crossing the frontier, was confirmed Friday by NATO’s secretary general, Anders Fogh Rasmussen.

“I can confirm that last night we saw a Russian incursion, crossing of the Ukrainian border,” Mr. Rasmussen told journalists during a visit to Copenhagen, according to news agency reports. He did not elaborate on what had happened to the Russian vehicles.

But a statement on the website of Ukraine’s president, Petro O. Poroshenko, said that most of the Russian vehicles had been destroyed. The statement said Mr. Poroshenko had spoken by telephone with Prime Minister David Cameron of Britain about news media reports of a Russian military incursion and told him that “the given information was trustworthy and confirmed because the majority of the machines had been eliminated by Ukrainian artillery at night.” It gave no details.