Kyiv has launched a major push to dislodge Russian forces from southeastern Ukraine as part of its weeks-long counteroffensive, committing thousands of troops to the battle in the country's southeast, according to Western and Ukrainian officials and analysts.

The surge in troops and firepower has been centered on the southeastern Zaporizhzhia region, a Western official said late Wednesday.

The official was not authorized to comment publicly on the matter and spoke on condition of anonymity.

Fighting has intensified in recent weeks at multiple points along the 1,500-kilometre (930-mile) front line as Ukraine deploys Western-supplied advanced weapons and Western-trained troops against the deeply entrenched Russian forces who invaded 17 months ago.

Ukrainian officials have been mostly silent about battlefield developments since they began early counteroffensive operations, though Deputy Defence Minister Hanna Maliar said troops are advancing toward the city of Melitopol in Zaporizhizhia region.

Though that movement could be a tactical feint, and both governments have used disinformation to gain battlefield advantages, such a maneuver would be in line with what some analysts had predicted.

They envisioned a counteroffensive that would try to punch through the land corridor between Russia and the Russian-annexed Crimean peninsula, moving towards Melitopol, which is close to the coast of the Azov Sea.

That could split Russian forces into two halves and cut off supply lines to the units that are located further to the west.

The intense fighting is taking place in areas in the south and east of Ukraine, far from the capital Kyiv, and it was not possible to verify either side's claims.

The Institute of Study of War, a Washington-based think tank, reported that Ukrainian forces launched “a significant mechanised counteroffensive operation in western Zaporizhzhia region” on Wednesday, adding that they “appear to have broken through certain pre-prepared Russian defensive positions.”

It cited Russian sources, including the Russian Ministry of Defense and several prominent Russian military bloggers.

US officials, who have provided Kyiv with weapons and intelligence, declined to comment on the latest developments, though they have previously urged patience as Ukraine seeks to grind down the deep Russian defences featuring minefields, trenches and anti-tank obstacles.

US Defence Secretary Lloyd Austin said during a visit to Papua New Guinea that Kyiv's effort to retake land seized by Russia since its February 2022 full-scale invasion would be “tough” and “long,” with successes and setbacks.

US Secretary of State Antony Blinken said “an intense battle” is taking place but declined to provide details.

“We believe that tools, the equipment, the training, the advice that many of us have shared with Ukrainians over many months puts them in good position to be successful on the ground in recovering more of the territory that Russia has taken from Ukraine,” Blinken said during a visit to New Zealand.