Nearly three months since launching a much vaunted counteroffensive using hundreds of billions of dollars of Western military equipment, Ukraine has recaptured more than a dozen villages but has yet to penetrate Russia's main defences.

Stories in the New York Times, Washington Post and other news organisations last week quoted U.S. and other Western officials as suggesting the offensive was falling short of expectations. Some faulted Ukraine's strategy, including blaming it for concentrating its forces in the wrong places.

Moscow says the Ukrainian campaign has already failed. Ukrainian commanders say they are moving slowly on purpose, degrading Russia's defences and logistics to reduce losses when they finally attack at full strength.

"Criticising the slow pace of (the) counteroffensive equals ... spitting into the face of (the) Ukrainian soldier who sacrifices his life every day, moving forward and liberating one kilometre of Ukrainian soil after another," Ukraine's Foreign Minister Dmitro Kuleba told reporters on Thursday.

"I would recommend all critics to shut up, come to Ukraine and try to liberate one square centimetre by themselves," he said at a meeting of EU foreign ministers in Spain.

NATO Secretary-General Jens Stoltenberg told CNN that Ukrainian commanders deserved the benefit of the doubt.

"Ukrainians have exceeded expectations again and again," he said. "We need to trust them. We advise, we help, we support. But... it is the Ukrainians that have to make those decisions."

DEFENSIVE LINES

After months of fighting their way through heavy minefields, Ukraine's forces have finally reached the main Russian defensive lines in recent days, south of the village of Robotyne which they captured last week in Western Zaporizhzhia region.

They are now advancing in an area between the nearby villages of Novopokropivka and Verbove, looking for a way around the anti-tank ditches and rows of concrete pyramids known as dragon's teeth that form Russia's main fortifications visible from space.

A breakthrough there would provide the first test of Russia's deeper defences, which Ukraine hopes will be more vulnerable and less heavily mined than the areas its troops have traversed so far.

A Ukrainian commander in the area told Reuters last week that his men had already breached the most difficult line, reaching areas that were less heavily defended, and now expected to advance more quickly. Reuters could not independently verify this.

Kyiv rarely gives details of its offensive operations. In a statement on Thursday, deputy defence minister Hanna Maliar reported unspecified successes near Novopokropivka, without giving details.

Oleksandr Syrskyi, commander of Ukraine's ground forces, also reported a "positive dynamic" in the east near Bakhmut, where Ukrainian forces have been advancing around the only city Russia captured in its own offensive earlier this year.

DRONE ATTACKS WITHIN RUSSIA

Ukraine has also stepped up attacks using drones on targets deep within Russia itself and in Russian-controlled territory in Ukraine. Russia reported overnight drone attacks in neighbouring Bryansk region late on Wednesday, and said it had shot down a missile fired on occupied Crimea.

The previous night, Moscow reported attempted Ukrainian drone strikes in six Russian regions, including one that caused a huge fire at a military air base in Pskov in northern Russia, damaging several giant military transport planes on the tarmac.

While Ukraine rarely comments directly on specific attacks inside Russia, President Volodymyr Zelenskiy appeared to boast of the Pskov attack on Thursday.

"Successful use of our long-range weapons: the target was hit 700 kilometres away!" he said in an online post.

Ukraine's Western allies generally forbid Kyiv from using weapons they supply to attack Russian territory, but say Ukraine has a right to carry out such attacks on military targets with its own weapons.

The attacks in recent weeks, including several on central Moscow over the past month, have brought the war home to many Russians for the first time after 18 months during which Russia has subjected Ukraine to countrywide air strikes.

Russia is also facing the aftermath of a mutiny two months ago by Wagner, a private army that had formed the main attack force of its own winter offensive earlier this year. Wagner's leader Yevgeny Prigozhin and his main lieutenants were killed in an air crash last week.

The Kremlin has denied that it was behind the crash. President Vladimir Putin had called Prigozhin's mutiny treason but had promised not to punish him for it.

On Thursday Prigozhin's right-hand man, Dmitry Utkin, a neo-Nazi former military intelligence officer whose call-sign Wagner gave the mercenary force its name, was buried at a cemetery near Moscow under heavy guard of Russian military police. Prigozhin was similarly buried on the outskirts of St Petersburg on Tuesday.