TOP WRAP 8-Rockets hit Lviv in western Ukraine, Biden calls Putin a 'butcher'

(Adds details from Lviv, Kremlin)

* Russian forces take town near Chernobyl at second attempt

* Russia signals military focus on eastern Ukraine

* Ukrainian president warns of Russia energy 'blackmail'

* U.S. president meets Ukrainian ministers in Warsaw

By Natalia Zinets

LVIV, Ukraine, March 26 (Reuters) - Rockets struck the outskirts of the western Ukrainian city of Lviv on Saturday for what appeared to be the first time since Russia's invasion, and Russian forces took control of a town where workers at the defunct Chernobyl nuclear plant live.

Intense fighting raged in several parts of Ukraine, suggesting there will be no swift let-up in the month-old war, and U.S. President Joe Biden called Russian President Vladimir Putin a "butcher" after meeting Ukrainian refugees in Poland.

The Kremlin was cited by Russia's TASS news agency as saying such comments would further damage prospects for mending Russian-U.S. ties.

After more than four weeks of fighting, Russia has failed to seize any major Ukrainian city and the conflict has killed thousands of people, sent nearly 3.8 million abroad and driven more than half of Ukraine's children from their homes, according to the United Nations.

Moscow signalled on Friday it was scaling back its military ambitions to focus on territory claimed by Russian-backed separatists in the east

But two rockets hit the outskirts of Lviv, some 60 km (40 miles) from the Polish border, a city that so far have escaped the heavy bombardment and fighting that has devastated some Ukrainian cities closer to Russia.

Regional Governor Maksym Kozytskyy said five people had been wounded and residents were told to head to shelters after three powerful blasts in mid-afternoon. Reuters witnesses saw black smoke rising from the northeast side of the city and Lviv's mayor said an oil storage facility had been hit.

Russian troops seized Slavutych, a town where workers at the nearby Chernobyl plant live, the regional governor said.

He said Russian forces had fired into the air and thrown stun grenades to disperse residents who unfurled a large Ukrainian flag and shouted "Glory to Ukraine" in protest. Reuters could not independently verify the reports.

Slavutych sits just outside the so-called exclusion zone around Chernobyl, which was the site of the world's worst nuclear disaster in 1986.

Ukrainian staff have continued to work at Chernobyl after the plant was seized by Russian forces soon after the start of the Feb. 24 invasion, and the International Atomic Energy Agency (IAEA) has expressed alarm about the situation if workers are unable to rotate.