Ukraine claims it broke through part of Russia's fearsome defensive line in its counterattack. The next layer is even worse.

• Ukraine said it broke through Russian defensive lines in the south of the country.
• But troops are now coming up against concrete fortifications Russia has built.

Ukraine has said its troops broke through Russian defense lines in the south of the country in a rare success for its counteroffensive.

But by Ukraine's own admission, the next stage of the attack will be harder still.

The country's deputy defense minister, Hanna Maliar, gave an update on operations, claiming that the Russian defenses had been pierced — she did not give a precise location.

Anton Gerashchenko, an influential advisor to the Ukrainian government, posted footage of her update to social media.

She went on to say that Russia had made further layers of defenses that would be tough to crack.

She said that Russian soldiers have built concrete fortifications on high ground, which could make it hard to advance. She also cited artillery bombardment and minefields as significant obstacles.

Maliar also said that Russia was drawing on additional resources and combat reserves in the south and the east.

Ukraine's much-anticipated counteroffensive has only made marginal gains in two months.

Russia's elaborate defensive lines have proven more effective than expected, particularly its minefields, barricades, and anti-tank traps.

In some areas, the dense minefields have forced Ukrainian soldiers to leave behind their Western tanks and progress on foot.

Ukrainian officials have said that its troops were at a disadvantage because the Western weapons they needed to help them advance took so long to arrive that Russia was able to prepare for them.