(Adds Zelenskiy on gains in south, probe of damaged pipelines)
Rescuers help people escape from rubble after strike
Attack a reminder of Russia's missile capabilities
Ukraine says it takes more territory in the south
Public criticism of Russian top brass mounts
By Jonathan Landay and Pavel Polityuk
BAKHMUT, Ukraine/KYIV, Oct 6 (Reuters) - A missile demolished an apartment block on Thursday in a Ukrainian region that Moscow says it has annexed, killing seven people, a Ukrainian official said, as discontent mounted within Russia about the handling of the war by the top brass.
The missile attack on the city of Zaporizhzhia in the southern region of the same name left some people buried under rubble, the regional governor said. He added at least five people are missing.
There was no immediate comment from Russia, whose invasion of Ukraine has begun to unravel after a Ukrainian counteroffensive in which thousands of square miles of territory have been retaken since the start of September, including dozens of settlements in recent days.
Thousands of Russian troops have retreated after the front line crumbled, first in the northeast, and, since the beginning of this week, also in the south. Ukraine's President Volodymyr Zelenskiy said in a video address on Thursday that Kyiv's forces recaptured more than 500 square kilometres (195 square miles) of territory and dozens of settlements in the southern Kherson region alone in October.
Reuters could not independently verify battlefield accounts.
In rare, but growing, public criticism of Russia's top military officials, Kirill Stremousov, the deputy head of the Russian-backed administration in Kherson region, slammed "generals and ministers" in Moscow for failing to understand the problems on the front lines.
There was no immediate comment from Russia's defence ministry.
Discontent has begun to bubble up among even loyalist state TV hosts.
"Please explain to me what the general staff's genius idea is now?" Vladimir Solovyov, one of the most prominent Russian talk show hosts, said on his livestream channel.
"Do you think time is on our side? They (the Ukrainians) have hugely increased their amount of weapons... But what have you done in that time?"
RUBBLE, SMOKE AND DUST
Images of the aftermath of Thursday's missile strike showed a gaping, rubble-strewn hole where a five-storey apartment block used to stand next to a wine shop.
Reuters reporters saw firefighters bringing a father and son down a ladder and talking to an older man still trapped under rubble.
Eduard, a 49-year-old man who survived the attack, said he was woken at around five in the morning by a strong explosion. "The room filled with smoke and dust. I jumped up to go see what had happened," he said.
Regional governor Starukh said emergency crews had rescuyed 21 people. He had earlier put the number of injured at 12, including a three-year-old child.
In an online address to new security and energy co-operation forum the European Political Community, Zelenskiy accused Russia of deliberately targeting the same spot twice in succession.
"In Zaporizhzhia, after the first rocket strike today, when people came to pick apart the rubble, Russia conducted a second rocket strike. Absolute vileness, absolute evil."
Moscow says it does not deliberately target civilians.
In remarks to Australia's Lowy Institute, Zelenskiy said NATO should launch preventive strikes on Russia to preclude its use of nuclear weapons. Kremlin spokesman Dmitry Peskov denounced the comments as "an appeal to start yet another world war with unpredictable, monstrous consequences," according to RIA news agency.
The Zaporizhzhia missile attack came a day after Putin signed a law to incorporate four partially occupied Ukrainian regions into Russia, including Zaporizhzhia, in Europe's biggest attempted annexation since World War Two.
Kyiv called the new law the act of a "collective madhouse".
Russia moved to annex the regions after holding what it called referendums – votes denounced by Kyiv and Western governments as illegal and coercive.
In the Kharkiv region in the northeast, a Ukrainian general said on Thursday that Kyiv's forces had advanced up to about 55 km (34 miles) over the last two weeks.
In the eastern Donetsk region, the Ukrainian General Staff said Russian troops had blown up a dam near the city of Sloviansk as they withdrew, inundating the nearby town of Raihorodok. Reuters could not confirm the report independently.
Russian forces remained dug in around the nearby battered city of Bakhmut.
Separately, Sweden's security service said an underwater crime scene investigation of the energy pipelines linking Russia and Germany via the Bastic Sea found evidence of detonations and strengthened suspicions of sabotage.
The Nord Stream 1 and 2 gas pipelines were damaged early last week. Europe, which used to rely on Russia for about 40% of its gas, is facing an energy crisis.
Moscow has sought to pin the blame for the pipeline damage on the West, suggesting the United States stood to gain if Russia could not transfer gas to Europe. Washington has denied any involvement.
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(Reporting by Reuters bureaux; Writing by Andrew Osborn, Hugh Lawson and Cynthia Osterman; Editing by Alex Richardson and Andrew Heavens and Aurora Ellis)