After weeks of preparation, the Ukrainian army may finally have launched the bulk of its offensive in an attempt to break through the Russian defenses in the hope of a success that is vital for the continuation of the war. Russian officials and independent bloggers say Ukrainian troops -- backed by tanks, artillery and drones -- are trying to advance south of the town of Orikhiv for the second night running. Russia said on Friday that it had repelled several Ukrainian attacks in southern Ukraine, particularly in the Zaporizhzhia region. "Over the last 24 hours, Ukrainian forces have continued their attempts to carry out offensives in the Yuzhno-Donetsk and Zaporizhzhia regions", the Russian Ministry of Defense said in a statement, assuring that these had been repelled thanks to "decisive actions (...) by Russian forces units". Many observers, including the American analysis center Institute for the Study of War (ISW), believe that "the Ukrainian counter-offensive has begun", although they do not expect "a single major operation" but a series of different coordinated actions, as is currently the case. Several military experts have said the focus of Ukraine's long awaited counter-offensive will be Zaporizhzhia. They argue Kyiv is trying to regain access to the Sea of Azov, splitting the occupying Russian forces in the region into two detached groupings. That would not only weaken Russia's combat capability but also eliminate a land bridge to Crimea, the southern peninsula illegally annexed by Russia in 2014. Ukraine has been planning a counter-offensive for months, but it has wanted as long as possible to train troops and to receive advanced military equipment from Western allies. The government is deliberately saying little about its plans but its forces are now probing Russian positions at several points along the front line, looking for signs of weakness. Meanwhile Russian attacks on Ukraine continue. Overnight it launched fresh cruise missile and drone strikes, with falling debris killing at least one person in Zhytomyr to the west of the capital Kyiv. Russia seized most of the Zaporizhzhia region soon after President Vladimir Putin ordered a full-scale invasion in February 2022. However the regional capital, the city of Zaporizhzhia, is controlled by Ukraine. The recent fierce fighting in the area continued overnight, with several Russian pro-Kremlin military bloggers reporting late on Thursday that Ukraine had resumed attacks, noting the movement of armoured personnel carriers and drones directing artillery fire. Vladimir Rogov, a Russian-installed local official, said Russian troops were holding their positions amid "active fighting" towards the city of Tokmak, seen as a key target for Ukraine as it seeks to advance to the Sea of Azov. It is difficult to verify the competing claims by both sides. Earlier on Thursday Ukraine's Deputy Defence Minister Hanna Maliar said Russian forces were currently "in active defense" in Zaporizhzhia and claimed advances were being made around the eastern city of Bakhmut, which has been largely destroyed during months of fighting. The Zaporizhzhia region is also home to Europe's largest nuclear power plant, which is in an area controlled by Russian forces. — Agencies