KYIV, July 27 - Fierce fighting raged Thursday in southeastern Ukraine, where a Western official said Kyiv has launched a major push and Russian President Vladimir Putin said “hostilities have intensified significantly,” The Associated Press reported.

Battles in recent weeks have taken place on multiple points along the over 1,000-kilometer (600-mile) front line as Ukraine wages a counteroffensive with Western-supplied weapons and Western-trained troops against Russian forces who invaded 17 months ago.

President Volodymyr Zelenskyy congratulated his troops on reclaiming control of a village, while Putin praised Russian troops “heroism” in repelling attacks in the southeastern Zaporizhzhia region.

Putin insisted on state TV that the Ukrainian troops’ push “wasn’t successful” and charged that they suffered heavy casualties, although it was not possible to independently verify his claim. Putin was in St. Petersburg at a summit of African leaders.

Ukrainian troops have made only incremental gains since launching a counteroffensive in early June, and Putin has repeatedly claimed Ukraine has suffered heavy losses, without offering evidence.

Ukraine has committed thousands of troops in the region in recent days, said a Western official who was not authorized to comment publicly on the matter.

A U.S. official said Ukraine has begun to commit troops from the 10th Corps, although it’s not certain all of its units are moving into the fight. Ukraine had been holding the 10th Corps in reserve, with the expectation it would be used to exploit gaps or soft spots the ground forces opened up. Those additional new forces would be used to take advantage of places where Ukrainian troops have been able to break through some of Russia’s defenses.

The U.S. official spoke on condition of anonymity to discuss ongoing military operations.

Gen. Mark Milley, chairman of the Joint Chiefs of Staff, told Pentagon reporters last week that Ukraine was “preserving their combat power” and that a “significant” amount of it had not yet entered action as Ukrainian forces slowly and deliberately worked their way through the Russian minefields.

It was unclear how the current effort differs from previous ones by the Ukrainian military to break through deeply entrenched Russian defenses. The Russian army has set up vast minefields to stymie Ukrainian advances and used combat aircraft and loitering munitions to strike Ukrainian armor and artillery.

Zelenskyy posted a video Thursday in which a group of Ukrainian soldiers said they had taken control of the village of Staromaiorske in the Donetsk region next to the Zaporizhzhia province. “Our South! Our guys! Glory to Ukraine!” Zelenskyy declared.

Russian military bloggers have confirmed that Ukrainian forces have taken part of the village that was the focus of Ukraine’s attacks in recent days. If Russian defenses in the area collapse, it would open the way for the Ukrainian forces to push southward toward the coast.

Ukrainian authorities have kept operational details of the counteroffensive under wraps, and they have released scant information about its progress.

However, Deputy Defense Minister Hanna Maliar said Wednesday that troops are advancing toward the city of Melitopol in the Zaporizhizhia region.

The seizure of Melitopol near the Sea of Azov would be a major success for Ukraine, which hopes to punch through the land corridor between Russia and the Crimean Peninsula, illegally annexed by Moscow in 2014. That could split Russian forces into two and cut supply lines to units farther west. Russia currently controls the whole Sea of Azov coast.

The Institute of Study of War, a Washington-based think tank, reported that Ukrainian forces launched “a significant mechanized counteroffensive operation” in western Zaporizhzhia on Wednesday and “appear to have broken through certain pre-prepared Russian defensive positions.” (ap/ez)