Russia pounded gas production facilities and a major missile factory in new missile strikes on critical infrastructure in Ukraine.
Explosions were heard in several parts of the country on Thursday, including the southern port of Odesa, the capital Kyiv and the central city of Dnipro, and civilians were urged to take shelter as air raid warnings were issued.
Targets included the huge Pivdenmash missile factory in Dnipro, Prime Minister Denys Shmyhal said.
"Missiles are flying over Kyiv right now. Now they are bombing our gas production facilities, they are bombing our enterprises in Dnipro and Pivdenmash," Interfax Ukraine news agency quoted him as telling a conference.
It was not immediately clear which gas production facilities he was referring to.
Russia has stepped up attacks on Ukrainian energy facilities in recent weeks, launching some of the heaviest waves of missile strikes since invading Ukraine on February 24.
Ukraine has said that its air defences have knocked out many of the missiles and drones fired in the last few weeks.
Kyiv city officials said two cruise missiles and four Iranian-made Shahed drones were destroyed near the city on Thursday.
There was no immediate word of any deaths in the new wave of air strikes.
"This morning Russia launched another missile barrage at Ukraine's critical infrastructure," Foreign Ministry spokesperson Oleg Nikolenko said.
"(Russian President Vladimir) Putin wants to deprive millions of people of electricity and heating, amid freezing temperatures.
Send Ukraine more air and missile defence systems to avert this tragedy. Delays cost lives."