Ukraine’s military advanced as much as 30 miles in the country’s east and liberated more than 20 villages and towns, a senior commander said, in a rapid thrust aimed at cutting Russian supply routes.

Brig. Gen. Oleksiy Hromov, a senior officer on Ukraine’s General Staff, gave the first official confirmation of the gains of an offensive launched Tuesday to the east of Ukraine’s second-largest city of Kharkiv.

He told reporters in Kyiv that Russian forces were demoralized but resisting, and noted smaller advances near other eastern cities.

Russian authorities haven’t commented on the Ukrainian advance. But Gen. Hromov’s comments tally with reports from Russian war bloggers close to the Russian military who have said Ukrainian forces are making gains toward Kupyansk, a city of some 30,000 before the war, that is a critical road hub for the resupply and movement of Russian occupation forces.

Russian occupation authorities in Kupyansk said they would evacuate women and children from the strategic city as advancing Ukrainian forces stepped up strikes there.

The unexpected Ukrainian thrust appears to mark a new phase in the war where Kyiv is seeking to take back ground that Russia seized since it launched a full-scale invasion about six months ago. After repelling Russian forces from Kyiv in spring, Ukraine’s military has been gradually withdrawing from cities in the east under devastating artillery and airstrikes.

But the Russian advance there appears exhausted, and Ukraine has seized the initiative in the war with dual offensives in the south and east. In the south, Ukraine is seeking to cut off thousands of Russian troops on the western bank of the Dnipro River in and around the regional capital of Kherson.

To the east of Kharkiv, Kupyansk has emerged as a key target. Liberating the city, or even being close enough to use artillery to disrupt Russia’s supply lines, could isolate Russian forces in the city of Izyum to the south, which Moscow had sought to use for an offensive of its own.

Russian war bloggers said Ukrainian forces were battling for control of the eastern city of Balakliya Thursday after surrounding it, and were also advancing to the northeast in the direction of Kupyansk, seizing villages.

Ukrainian President Volodymyr Zelensky hailed advances in his nightly address Wednesday but said he wouldn’t disclose details. “This week we have good news from Kharkiv province,” he said. “I think every citizen feels pride for our warriors.”

U.S. Defense Secretary Lloyd Austin said Thursday that the U.S. is sending Ukraine $675 million in new military assistance.

Russian officials have dismissed indications that their six-month invasion is faltering. Russian President Vladimir Putin said Wednesday: “We have not lost anything and will not lose anything.”

A senior Russian official proposed holding votes on joining Russia in occupied territories on Nov. 4, a Russian public holiday known as National Unity Day. Andrei Turchak, leader of the governing United Russia party, said it would be a “correct and symbolic” date for the votes. He said they would certainly take place before the end of the year.

Russia had previously indicated that votes would take place in September, but those plans appear to have been scuttled by Ukraine’s offensives.

In areas that Russia has captured, Moscow has been handing out passports, taking control of schools and introducing the Russian ruble.

But occupation forces have met with resistance. Vladimir Rogov, a senior collaborator in occupied Melitopol in Ukraine’s south, said the headquarters of his group “We Are Together with Russia” had been blown up Wednesday.