KYIV — The Russian occupation authorities in Ukraine's southern city of Kherson have postponed a so-called referendum on joining Russia, on security grounds.

"This is being paused because of the security situation," said Kirill Stremousov, deputy head of the Russian-appointed administration there.

He said heavy Ukrainian shelling had made a key Kherson bridge impassable.

Ukraine and its Western allies have denounced the referendum plans in Kherson and other areas as illegal.

Meanwhile, Ukraine says its forces have recaptured Vysokopillya, a small town some 167km (104 miles) north of central Kherson.

That gain - not verified independently - is part of a counter-offensive in the south launched by the Ukrainian army last week.

A photo shows soldiers apparently raising the Ukrainian flag over the town, which had nearly 4,000 residents before the war. It was posted on Facebook by Kyrylo Tymoshenko, deputy head of President Volodymyr Zelensky's office.

His photo caption says: "Vysokopillya, Kherson Region. Ukraine. Today."

President Zelensky said Ukrainian forces had recaptured two "population centers" in the south, but did not name them.

Russia has been planning referendums in Kherson and the southern Zaporizhzhia region, most of which it controls.

Speaking on Russian state TV, Stremousov said Ukrainian shelling had damaged Kherson's Antonovskiy Bridge to such an extent that vehicles could no longer cross it.

He said barges transporting civilians across the Dnieper (Dnipro) river were also coming under Ukrainian fire, as was the city's infrastructure.

The Russians have relied on the bridge to bring troops and hardware in and out of Kherson.

Ukraine has deployed US-made Himars multiple rocket launchers in its drive to push the Russians out of the city - the first to fall to them after their 24 February invasion.

As well as Kherson, Russia has announced plans for referendums in other captured territory, similar to that held in Crimea after its troops seized the peninsula in 2014.

Ukraine's Deputy Prime Minister Iryna Vereshchuk urged civilians to leave Kherson as fighting intensifies in the area. She has also warned that any who participate in the planned Russian referendum are liable to face Ukrainian prosecution.

Russia's invasion has destabilized life in Ukraine to such an extent that it is not clear who could vote in such referendums anyway. The Crimea vote in 2014, held under military occupation, was not recognized internationally. — BBC