Ukrainian attacks in the key southern Zaporizhzhia district are proceeding, Russian authorities and military bloggers say, reporting heavy fighting there.

They say Ukrainian soldiers - backed by tanks, artillery, and drones - are trying to advance south of the town of Orikhiv for the second night running.

A senior Ukrainian defense official said the enemy was in "active defense".

A few military specialists have said the focus of Ukraine's long-awaited counter-offensive will be Zaporizhzhia.

They argue Kyiv is attempting to recover access to the Sea of Azov, parting the occupying Russian powers in the area into two detached groupings. That would weaken their combat capabilities.

Earlier on Thursday, the US-based Institute for the Study of War (ISW) said Ukraine's counter-offensive had begun - although Kyiv remains tight-lipped on the issue.

Meanwhile, the UK defense ministry said that "amidst a highly complex operational picture, heavy fighting continues along multiple sectors of the front".

It added that "in most areas, Ukraine holds the initiative".

Russia seized most of the Zaporizhzhia region - including Europe's largest nuclear power plant - soon after President Vladimir Putin ordered a full-scale invasion in February 2022.

The regional capital, the city of Zaporizhzhia, is controlled by Ukraine.

Several Russian pro-Kremlin military bloggers reported late on Thursday that Ukraine had resumed its attacks overnight.

They said armored personnel carriers and drones directing artillery fire were also deployed.

Vladimir Rogov, a Russian-installed local official, said there had been "active fighting" in the area between Orikhiv and Tokmak, with Russian troops holding their positions.

The town of Tokmak is seen by many military experts as a key target for Ukraine as it seeks to advance to the Sea of Azov.

Russian Defence Minister Sergei Shoigu said the earlier reported Ukrainian assault had been repelled, harming the enemy. The minister provided no evidence to back his claim.

Meanwhile, Ukraine's Deputy Defence Minister Hanna Maliar said in a brief statement on Thursday that Russian forces were currently "in active defense" on the Zaporizhzhia direction.

In its latest bulletin on Thursday evening, Ukraine's military stated only that the "enemy continues to be on the defensive" towards Zaporizhzhia as well as in neighboring Kherson, a region hit by massive flooding after a major dam collapsed earlier this week.

The Ukrainian military added that Russian troops had carried out air strikes there and used artillery during the day.

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.

Last month, Oleksiy Danilov, secretary of the National Security and Defence Council of Ukraine, told the BBC that Kyiv was ready to launch the attack - without naming a specific date.

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