Ukrainian forces believe they have broken through the most difficult line of Russian defences in the south and will now be able to advance more quickly, a commander fighting in the south told Reuters.
Ukraine launched a counteroffensive in June, but well-prepared Russian defence lines reinforced by minefields have slowed their southward advance towards the Sea of Azov.
Ukrainian forces said on Wednesday they had raised the national flag in the settlement of Robotyne in the southern Zaporizhzhia region, about 10 km (six miles) south of the frontline town of Orikhiv.
"We don't stop here," said a commander who led some of the troops into Robotyne and uses the nom de guerre "Kombat".
"Next we have (the town of) Berdiansk, and then more. I made it clear to my fighters at once: our goal is not Robotyne, our goal is (the Sea of) Azov."
Robotyne is about 100 km from Berdiansk, a port on the shores of the Sea of Azov, and 85 km from the strategic city of Melitopol. Both are occupied by Russian forces following Moscow's full-scale invasion in February last year.
Moscow has not confirmed that Ukraine has advanced into Robotyne.
A U.S. official said last week that Ukrainian forces did not appear likely to be able to reach and retake Melitopol in their counteroffensive, intended to split Russian forces in the south.
"We have passed the main roads that were mined. We are coming to those lines where we can go (forward). I'm sure we'll go faster from here," Kombat said.
He said two houses were still under Russian control in Robotyne: "We're fighting for them, and then we'll have full control (of Robotyne)."
Kombat said Ukrainian troops had now entered territories where there were only "Russian logistics" groups, and where he made clear he did not expect Russian defences to be as difficult to break through.
"We are moving on to liberate all our territories," he said.
