•Addressing lawmakers in Luxembourg, he added that the front line extended for more than 1,000km (621 miles).
•Russian forces have been intensifying attacks on the city of Severodonetsk in the eastern Donbas region.
Image: REUTERS
Ukraine's President Volodymyr Zelensky says that Russian forces have seized 20% of his country's territory, as Moscow's invasion nears its 100th day.
Addressing lawmakers in Luxembourg, he added that the front line extended for more than 1,000km (621 miles).
"All combat-ready Russian military formations are involved in this aggression," he told MPs via videolink.
Russian forces have been intensifying attacks on the city of Severodonetsk in the eastern Donbas region.
UK defence officials say Russia has seized most of the city and are making "steady local gains, enabled by a heavy concentration of artillery".
Severodonetsk is the easternmost city under Ukrainian control and regional governor Serhiy Haidai said Russia was trying to break through defences in the city "from all directions".
However he said Ukrainian troops were carrying out counter-attacks, "pushing back the enemy on some streets and taking several prisoners".
Intense street-to-street fighting in the city had hampered evacuations, he said, describing such efforts as "extremely dangerous".
Some 15,000 civilians remain trapped in Severodonetsk, with many of them taking shelter at the massive Azot chemical plant.
On Wednesday, Mr Zelensky accused Russia of "madness" after its troops allegedly targeted the site during an artillery barrage.
Further south, the mayor of the occupied city of Mariupol has accused Russian forces of executing civil servants who have refused to collaborate with the new Moscow-backed city authority.
Vadym Boychenko, who was evacuated from Mariupol before it fell, said dozens of residents were being held at the Olenivka Prison and that he had received reports of locals being tortured by occupying forces. The BBC cannot verify these allegations.
Last week an adviser to Mr Boychenko told CNN that at least 22,000 people had been killed during Russia's siege and bombardment of the city.
In the north-east, Russian shelling killed a woman and injured a man in Kharkiv, regional officials said.
And in western Ukraine five civilians were hurt in missile strikes on Lviv, regional head Maksym Kozytskyi said.
Western leaders are also stepping up sanctions against key allies of Russian President Vladimir Putin.
US Treasury Department officials unveiled a new raft of sanctions on Thursday, with targets including several yachts allegedly linked to Mr Putin and a cellist who allegedly acts as a middleman for the Russian leader.
US officials will seek to seize two vessels, the Russian-flagged Graceful and the Cayman islands-flagged Olympia, which were identified as personal assets of Mr Putin.
The cellist, Sergei Roldugin, is allegedly a custodian of the Russian president's offshore wealth.
Five oligarchs with links to Mr Putin as well as Russian foreign ministry spokesperson Maria Zakharova will also have any US assets frozen and are barred from doing business with US-based corporations.
EU diplomats are said to have finalised a sixth package of sanctions against Moscow.
The sanctions, which include a limited ban on Russian oil imports, were reportedly agreed after officials accepted a Hungarian request to remove the Russian Orthodox Church, Patriarch Kirill, from the list of targets.
The president of the European Parliament also announced a ban on Russian lobbyists entering the chamber's campus.
Roberta Metsola wrote on Twitter that she was keen to deprive Moscow's representatives of the ability "to spread their propaganda & false, toxic narratives about the invasion of Ukraine".
On Wednesday President Joe Biden announced that the US would supply Ukraine with new long-range missiles capable of hitting targets at distances of up to 70km (45 miles).
Kremlin spokesman Dmitry Peskov accused the US and its allies of intentionally prolonging the war and of "adding fuel to the fire" with the deliveries.