Russian troops on Wednesday pressed closer to the centre of a factory city in their drive to grab a swathe of eastern Ukraine, while the United States said it would supply advanced rockets to Kyiv to help it force Moscow to negotiate an end to the war.
Ukraine's General Staff said Russian forces, now 98 days into their invasion, were pounding infrastructure in eastern and southern regions including the symbolically important industrial city of Sievierodonetsk, which they entered on May 27. It has been the main focus of their ground offensive for several weeks.
Sievierodonetsk is a Soviet-era city that houses a large chemical factory. According to the local governor, a Russian airstrike hit a large chemical plant in the city on Tuesday, blowing up a tank of toxic nitric acid.
Russia "attacked the Azot factory from a plane, resulting on the release of toxic substances," Governor Serhiy Gaidai said, urging residents to remain inside. Reuters could not independently confirm the cause of the incident.
President Joe Biden announced the supply of precision rocket systems and munitions that could strike at long-range Russian targets, part of a $700 million weapons package expected to be unveiled on Wednesday.
"We have moved quickly to send Ukraine a significant amount of weaponry and ammunition so it can fight on the battlefield and be in the strongest possible position at the negotiating table," Biden wrote in an opinion piece in the New York Times.
A senior Biden administration official said the new supplies - which comes on top of billions of dollars worth of equipment such as drones and anti-aircraft missiles - included the M142 High Mobility Artillery Rocket System (HIMARS), which Kyiv has said is "crucial" to counter Russian missile attacks.
Ukraine welcomed the West's supply of weapons, which has included M777 howitzers deployed along the frontline in the Luhansk region that includes Sieverodonetsk, although regional governor Gaidai decried a "rose-coloured" view of the situation.
"Weapons are coming but not in the volumes we wanted," he said. "There will be no victory just in an instant because of the 777 howitzer."
Addressing concerns that weapons such as HIMARS could draw the United States into direct conflict, senior administration officials said Ukraine had given assurances the missiles would not strike inside Russia.
Russia, however, warned of an increased risk of direct confrontation with the United States. Deputy Foreign Minister Sergei Ryabkov told state news agency RIA Novosti that Moscow viewed the development "extremely negatively."
Shortly after the U.S. decision was announced, the Russian defence ministry said Russia's nuclear forces were holding drills in the Ivanovo province, northeast of Moscow, the Interfax news agency reported.
Some 1,000 servicemen were exercising in intense manoeuvres using more than 100 vehicles including Yars intercontinental ballistic missile launchers, it cited the ministry as saying.
There was no mention of the U.S. decision to supply new weapons in the Interfax report.
Russia has also completed testing of its hypersonic Zircon cruise missile and will deploy it by the end of the year on a new frigate of its Northern Fleet, a senior military officer said on Wednesday.
Ukraine's General Staff said Russian forces continued to pound northern, southern and eastern districts of Sievierodonetsk.
If Russia captures the city and its smaller twin Lysychansk on the west bank of the Siverskyi Donets river, it will hold all of Luhansk, one of two provinces in the eastern Donbas region that Moscow claims on behalf of separatists and a key war aim of President Vladimir Putin.
Russian forces now control about 70% of the city, said Gaidai. He has previously said the city has been largely reduced to rubble.
"Some Ukrainian troops have retreated to more advantageous, pre-prepared positions," Gaidai said. Lysychansk was easier to defend because it is located on a hill but Russian forces will target it with artillery and mortars once in full control of Sievierodonetsk, he said.
The leader of the pro-Moscow Luhansk People's Republic, Leonid Pasechnik, told TASS news agency Russian proxies had advanced slower than expected to safeguard city infrastructure and "exercise caution around its chemical factories".
Jan Egeland, head of the Norwegian Refugee Council aid agency which had long operated out of Sievierodonetsk, said up to 12,000 civilians remain trapped in the crossfire, without sufficient access to water, food, medicine or electricity.
Before the war, the city was home to around 120,000 people.
The new U.S. package includes ammunition, counter fire radars, a number of air surveillance radars, additional Javelin anti-tank missiles, as well as anti-armour weapons, officials said.
German Chancellor Olaf Scholz, accused by critics of dragging his feet in helping Ukraine, said on Wednesday Berlin would supply Kyiv with its IRIS-T medium-range surface-to-air defence system.
Ukrainian President Volodymyr Zelenskiy has called for more weapons while lambasting the European Union, which agreed on Monday to cut imports of Russian oil, for not sanctioning energy from Russia sooner.
The EU said it would ban imports of Russian oil by sea. Officials said that would halt two-thirds of Russia's oil exports to Europe at first, and 90% by the end of this year.
Responding to the EU oil embargo, Russia widened its gas cuts to Europe, driving prices higher and ratcheting up its economic battle with Brussels.
The war has disrupted Ukraine's exports of wheat and other commodities, hitting consumers with higher food prices especially in the world's poorest countries.
Pope Francis appealed on Wednesday for all blockades on wheat exports from Ukraine to be lifted, saying grain should not be used as a "weapon of war".
Putin launched what he calls a special military operation on Feb. 24 to disarm and "denazify" Ukraine. Ukraine and its Western allies call this a baseless pretext for a war of aggression.
(Reporting by Reuters bureaux; Writing by Stephen Coates and Gareth Jones; Editing by Lincoln Feast and Frank Jack Daniel)