Ukraine’s new NATO-standard tanks and fighting vehicles are appearing in battlefield images as military analysts said Kyiv’s long-awaited counteroffensive is underway.

German-made Leopard tanks and US Bradley Fighting Vehicles pushing toward the town of Tokmak, in Ukraine’s occupied south, showed up in photographs posted by Russian military bloggers that seem genuine, according to Osint Defender, an online open-source intelligence group that said it geolocated the images and checked for any signs they’d been manipulated.

The stills were taken from a Russian defense ministry video that showed a column of the vehicles moving into action and at least one being destroyed. Oryx, another online group that conservatively catalogues equipment losses on both sides added a first Leopard 2A4 tank to its list.

“The Ukrainian counteroffensive has begun,” said Ben Barry, senior fellow for land warfare at the London-based International Institute for Strategic Studies, in an emailed comment. “Since 4 June Ukrainian forces have been attacking along the front line. This seeks to pin Russian forces in place and probe for weaknesses.”

Ukraine is counting on the campaign to drive Russian forces from more of its territory, cementing support among its allies and heading off pressure from some other capitals for peace negotiations that would require it to give up ground. US and European governments have provided tens of billions of dollars in weapons and training for Ukrainian troops as they prepare to take on a Russian military that’s spent months digging into defensive positions.

It remains unclear whether the Ukrainian operations are the spearhead of a main attack or efforts to expose weak spots in Russian defenses, according to a European official.

Ukrainian forces made some advances in the south this week, but equipment losses also have been significant, the official said, speaking on condition of anonymity due to the sensitivity of the issue. Kyiv is widely expected to seek to cut the zone currently occupied by Russia into two, severing vital supply and communication lines for Moscow’s troops in Crimea.

“The counteroffensive won’t likely unfold as a single grand operation,” the Institute for the Study of War said Thursday. “It will likely consist of many undertakings at numerous locations of varying size and intensity over many weeks.” The Washington-based think tank said the initial phase may see the highest Ukrainian losses.

At least some Russian military bloggers continued to warn that Ukraine’s advances weren’t being recognized by officials in Moscow.

Russia’s Chief of General Staff Valery Gerasimov reported to President Vladimir Putin on Thursday that a Ukrainian force about a brigade strong had attacked during the night but failed to break through Russian defenses, according to a statement by Russia’s Defense Ministry. These claims couldn’t be independently verified.

Earlier in the week, the ministry released a video it said showed Russian helicopters destroying a Leopard tank, but independent analysts later said the footage showed they’d hit tractors and other farm equipment.

Ukrainian Deputy Defense Minister Hanna Malyar said Thursday that fighting was underway in the south and around the eastern city of Bakhmut but gave no additional information.

Deployment in numbers of the Leopard and Challenger 2 tanks, or infantry fighting vehicles such as Bradleys and German Marders that Ukraine received since December, would clearly signal a counteroffensive underway, according to Barry of the IISS.

He said that Russian military blogger reports from around Tokmak also would, if confirmed, suggest that at least one of Ukraine’s newly formed and equipped assault brigades has now been committed to the fight.

“Russia plans to fight linear defense battles from trench lines, exploiting obstacle belts, falling back on deeper defensive positions when pressed,” Barry said. “The key known unknown is the extent to which Russia has any credible reserve formations that can react to Ukrainian thrusts to block or counterattack.”

Ukraine has formed about nine assault brigades for the counteroffensive.

“Everything is just beginning,” Ivan Popov, commander of Russia’s 58th army, said on the Ministry of Defense Telegram channel. “We will prepare.”

--With assistance from Alberto Nardelli.

(Adds first confirmed loss of Leopard tank in third paragraph)