The frontline in Ukraine war shifted on Sunday as Russia made some advances in the fiercely contested eastern Donbas region and the Ukrainian military waged a counteroffensive near the strategic Russian-held city of Izium. In the west of Ukraine near the Polish border, missiles destroyed military infrastructure overnight and were fired at the Lviv region from the Black Sea, Ukrainian officials said. Ukrainian forces have notched up a string of successes since Russia invaded on February 24, forcing Russia’s commanders to abandon an advance on Kyiv and then making rapid gains in the northeast to drive them out of the second-biggest city Kharkiv. The largely Russian-speaking city with a pre-war population of 1.4 million is only 80 kilometres (50 miles) southwest of the Russian city of Belgorod, and was a key military objective earlier in the war, when Moscow hoped to capture and hold major cities. Russian embassy in US a ‘besieged fortress’, diplomats under threat: envoy Since mid-April, Russian forces have focused much of their firepower on Donbas after failing to take the capital. An assessment by British military intelligence issued on Sunday said Russia had lost about a third of the ground combat force deployed in February. Its Donbas offensive had fallen “significantly behind schedule” and was unlikely to make rapid advances during the coming 30 days, the assessment said. Russia’s forces continued to suffer “consistently high levels of attrition” while failing to achieve any substantial territory, Britain’s Defence Ministry said, adding that the forces are suffering “continued low morale and reduced combat effectiveness.” The officials said on Sunday that Moscow’s campaign in Ukraine, believed to have been launched with the goal of seizing Kyiv and toppling the Ukrainian government, had slowed to a snail’s pace. “The brutal invasion (by) Russia is losing momentum,” Nato Deputy Secretary-General Mircea Geoana said. “We know that with the bravery of the Ukrainian people and army, and with our help, Ukraine can win this war.” Moscow’s invasion, which it calls a “special operation” to disarm Ukraine and protect it from fascists, has jolted European security. Kyiv and its Western allies say the fascism assertion is a baseless pretext for an unprovoked war of aggression. Keeping up pressure on Izium and Russian supply lines will make it harder for Moscow to encircle battle-hardened Ukrainian troops on the eastern front in the Donbas. Izium straddles the Donets river, about 120km (75 miles) from Kharkiv on the main highway heading southeast. “The hottest spot remains the Izium direction,” regional governor Oleh Sinegubov said in comments aired on social media. “Our armed forces have switched to a counteroffensive there. The enemy is retreating on some fronts and this is the result of the character of our armed forces.” But Ukraine’s military acknowledged setbacks in an update on Sunday morning: “Despite losses, Russian forces continue to advance in the Lyman, Sievierodonetsk, Avdiivka and Kurakhiv areas in the broader Donbas region.” Both sides claimed success in military strikes in Donbas. The Ukrainian military said there was no let-up on Sunday in Russia’s bombardment of the steel works in the southern port of Mariupol, where a few hundred Ukrainian fighters are holding out weeks after the city fell into Russian hands. Zelensky said talks were underway seeking a way to evacuate wounded soldiers from Mariupol in return for the release of Russian prisoners of war. A large convoy of cars and vans carrying refugees from the ruins of the city arrived in Zaporizhzhia after nightfall on Saturday after waiting days for Russian troops to allow them to leave. Iryna Petrenko, a 63-year-old in the convoy, said she had stayed initially to take care of her 92-year-old mother, who subsequently died. “We buried her next to her house, because there was nowhere to bury anyone,” she said. Ukraine’s military has said Moscow is focused now instead on guarding supply routes, while launching mortar, artillery and air strikes in an attempt to deplete Ukrainian forces and destroy fortifications in the country’s east. As well as losing large numbers of men and much military equipment, Russia has been hit by economic sanctions. The Group of Seven industrial powers pledged on Saturday to “further increase economic and political pressure on Russia” and supply more weapons to Ukraine. On Sunday Germany ramped up shipments of heavy arms to Ukraine, sending self-propelled howitzers to Kyiv. Ukraine’s foreign minister Dmytro Kuleba praised Germany for setting a “precedent” and overcoming a “psychological barrier” by delivering heavy weapons to Kyiv. Kuleba said Germany had hosted training for Ukrainian soldiers on how to use the artillery. “This is an extremely important moment for our relations, because it will be the first heavy weapons that Germany will hand over to Ukraine soon,” he said. Berlin said it would send seven Pazerhaubitze 2000s (armoured howitzer 2000) to Ukraine, which Kuleba said would be used to “smash the enemy.” He had discussed what other weapons could be given to Kyiv, but “the final decision is still up to the Germans,” Kuleba said. Kuleba also discussed more weapon deliveries to Ukraine with US Secretary of State Antony Blinken in the German capital. “More weapons and other aid is on the way to Ukraine,” he said on Twitter, posting a photograph of his meeting with the US official.