Sky News is reporting Thursday that Ukrainian troops have used British Challenger 2 tanks during the ongoing cross-border offensive in Russia's Kursk region.

"While the UK and Ukraine governments remain tight-lipped on operational details, a source has signaled British tanks have crossed into Russia for Ukraine's Kursk offensive," the publication writes.

The Ukrainian armed forces' 82nd Air Assault Brigade had received up to 14 Challenger 2 tanks starting in January 2023. This highly provocative move condemned by Moscow later prompted Germany and the United States to also provide some tanks.

"According to government policy, the UK has confirmed Ukraine is free to use British weapons on Russian territory," Sky News reports. "A source said this included Challenger 2 tanks and signaled that they had been used during the Ukrainian incursion, which began on 6 August."

Sky News continues, "Details on how and when Ukrainian forces deployed Challenger 2 tanks within the Russian region of Kursk were not immediately clear. Neither was the number of tanks that may have been involved."

If confirmed, this certainly marks one of the single biggest escalations of the war and suggests that French, German, or American tanks might also cross the border into Russia. Already the Russian side has confirmed that its aerial forces took out Bradley Fighting Vehicles during the Kursk raid, which has been unfolding for more than a week.

The US has been among a few countries which have greenlighted Kiev forces' ability to use Western weapons to strike positions inside Russia, but only those areas from which strikes on Ukraine are launched.

The White House and Western allies have been vocal in supporting the Kursk operation, but the US claims it did not have foreknowledge of the invasion. President Biden on Tuesday told reporters, "I've spoken with my staff on a regular basis probably every four or five hours for the last six or eight days."