Firefighters doused the smouldering wreckage of the House of Culture in Dergachi, 10 km (six miles) north of Kharkiv, after what local officials said was an overnight Russian missile attack on the building used to distribute aid. Volunteers inside were trying to salvage packages of baby diapers and formula.

"I can’t call it anything but a terrorist act," the mayor, Vyacheslav Zadorenko, told Reuters. "They wanted to hit the base where we store provisions and create a humanitarian catastrophe."

Another missile had slammed into the building on Thursday and Russian shelling had wounded a staff member at a clinic and killed a young couple in their home, he said.

Russia, which denies targeting civilians, said its forces had shot down a Ukrainian Su-27 aircraft in the Kharkiv region and disabled the Kremenchuk oil refinery in central Ukraine.

It was not immediately possible to verify the reports.

Southeast of Kharkiv, Britain said Ukraine had stopped Russian forces crossing the Siverskyi Donets river west of Severodonetsk. Footage released by Ukrainian Airborne Forces Command appeared to show several burnt out military vehicles and segments of a bridge partially submerged in the river and many other damaged or abandoned vehicles, including tanks, nearby.

Reuters could not immediately verify the report, or when or where the clash took place.

The British defence ministry said Russia was investing significant military effort near Severodonetsk and Izium, and trying to break through towards Sloviansk and Kramatorsk to complete their takeover of Ukraine's industrial Donbas region.

Russian-backed separatists said they had taken the Zarya chemical plant in Rubizne near Severodonetsk.

The Kremlin calls its Feb. 24 invasion of Ukraine a "special military operation" to demilitarise a neighbour threatening its security. Ukraine says it poses no threat to Russia and that the deaths of thousands of civilians and destruction of cities and towns show that Russia is waging a war of aggression.

CHILDREN

Ukraine accused Russia of forcibly deporting more than 210,000 children since its invasion on Feb. 24, saying they were among 1.2 million Ukrainians transferred against their will.

The Kremlin says people have come to Russia to escape fighting.

In Kyiv, a court began hearing the first case of what Ukraine says are more than 10,000 possible war crimes; a Russian soldier is accused of murdering a civilian soon after the invasion. Moscow has accused Kyiv of staging such crimes. read more

In the southern port of Mariupol, Russian forces intensified their bombardment of the Azovstal steelworks, the last bastion of Ukrainian defenders in a city almost completely controlled by Russia after a siege of more than two months.

Reuters video showed explosions and thick smoke on Thursday and Ukrainian fighters released footage showing gunbattles. Some of the civilians evacuated recently from tunnels under the plant where they had taken shelter described terrifying conditions.

"Every second was hellish," 51-year-old nurse Valentyna Demyanchuk told Reuters. read more

Deputy Prime Minister Iryna Vereshchuk told 1+1 television negotiations were underway for the evacuation of wounded troops.

RUSSIAN SHIP SET ALIGHT

Renewed fighting around Snake Island in recent days may become a battle for control of the western Black Sea coast, according to some defence officials, as Russian forces struggle to make headway in Ukraine's north and east.

Ukraine said it had damaged a Russian navy logistics ship near the island, a small but strategic outpost close to Ukraine's sea border with Romania.

"Thanks to the actions of our naval seamen, the support vessel Vsevolod Bobrov caught fire - it is one of the newest in the Russian fleet," said Serhiy Bratchuk, a spokesman for the Odesa regional military administration.

Reuters could not independently verify the details. Russia's defence ministry did not immediately respond to a request for comment.

Satellite imagery from Maxar, a private U.S.-based company, showed the aftermath of what it said were probable missile attacks on a Russian Serna-class landing craft near the island, which became famous for the foul-mouthed defiance of its Ukrainian defenders early in the invasion.

NATO EXPANSION

As fighting continued around the country, wider diplomatic moves dialled up pressure on Russian President Vladimir Putin.

Foreign ministers from the G7 group of rich nations met to discuss a planned EU embargo on Russian oil as well as fears the conflict could spill over into Moldova.

Ukrainian Foreign Minister Dmytro Kuleba, who attended the meeting in Germany, said he hoped EU holdout Hungary would agree to the oil embargo and asked the G7 to hand over Russian assets to help Ukraine rebuild.

"We are talking about hundreds of billions of dollars. Russia must pay," he told reporters. read more

A day after Russia's northeastern neighbour Finland committed to applying to join NATO, Swedish Foreign Minister Ann Linde said membership for her country would have a stabilising effect and benefit countries around the Baltic sea. read more

Joining the 30-nation Western military alliance would end the neutrality the two states maintained throughout the Cold War and further the expansion of NATO that Putin said his invasion of Ukraine aimed to prevent.

Moscow called Finland's announcement hostile and threatened retaliation, including unspecified "military-technical" measures, but said a newspaper report the Kremlin might cut gas supplies to Finland was mostly likely a "hoax". read more

Russian supplies of energy to Europe remain Moscow's biggest source of funds and Europe's biggest source of heat and power.