KYIV — Ukrainian forces said they had penetrated the “first line” of Russian strongholds in the Zaporizhzhia region, in a sign that Kyiv is edging closer to Moscow’s sprawling network of fortified trenches along the southern front.

The Ukrainian military claimed on Thursday that its units had advanced towards two villages to the south and east of Robotyne, a village in Zaporizhzhia that Kyiv secured last week amid a grueling counteroffensive that is yielding incremental gains.

“In the Novodanylivka-Novoprokopivka direction, they have been successful, are consolidating their positions, inflicting artillery fire on the identified enemy targets, and conducting counter-battery operations,” the military’s general staff said on Thursday.

Testimonies reviewed by CNN shed light on the numerous challenges for Ukrainian troops trying to break through a dense system of Russian minefields, antitank obstacles and widespread tunnels in parts of southern and eastern Ukraine.

News of the latest progress comes against the backdrop of reports that US and Western allies had noted the slow pace of the counteroffensive. CNN reported earlier this month that the US had been receiving increasingly “sobering updates.”

Russian military bloggers reported increased activity near the village of Verbove, in southeastern Ukraine, but said Moscow’s forces were resisting Ukrainian advances.

On Monday, satellite imagery of the village of Solodka Balka – 7 kilometers (4 miles) south of Robotyne – showed steel-reinforced communications trenches, vehicle shelters and “dragon’s teeth” fortifications aimed at obstructing Ukrainian advances.

Kyiv has expanded its units towards the strategic town of Tokmak in recent weeks, a logistic center for Russian forces with a railhead through which resupply is carried out and depots for fuel and ammunition are situated.

Combat has ramped up towards the northern outskirts of Novoprokopivka – a small rural settlement about 4 kilometers (2.5 miles) south of Robotyne and close to a line of Russian fortifications in Zaporizhzhia, according to the 46th Brigade, which is fighting in the area.

“Bypassing the heights from the northeast made it possible to put pressure on the enemy’s right flank and reach its first line of defense, located on the heights to the south. The battles for the strongholds on them are ahead,” the brigade’s Telegram channel said.

Units were also stationed on the western edge of the village of Verbove, the brigade said on Telegram. Fighting was already taking place very close to Russian defensive lines, the brigade added.

“(The) Russians are constantly counterattacking and actively defending – we are moving, squeezing out the occupiers, but a month of fighting has shown that the enemy is not going to give up the captured land – there is a lot of work ahead.”

Two Ukrainian assault groups had tried to break through the defensive line on the outskirts of Verbove “and were destroyed,” the Russian-appointed official in control of occupied parts of Zaporizhzhia, Yevgeniy Balitsky, said.

Meanwhile, a well-known Russian military blogger, WarGonzo, said Ukrainian troops had advanced toward Verbove from the west but that Russian units “hold the defense on the outskirts of the settlement.”

Ukraine on Thursday reported multiple Russian air strikes in the area.

The 46th Brigade on Monday also reported heavy losses in the region, amid intense combat on the ground and the persistent use of artillery by both sides. — CNN