Ukrainian leaders have accused Russia of seizing 15 rescue workers and drivers from a humanitarian convoy trying to get desperately needed food and other supplies into the bloodied port city of Mariupol.
Ukrainian President Volodymyr Zelenskyy estimated that 100,000 civilians remained in Mariupol, scene of some of the war's worst devastation, as Russia presses a nearly month-old offensive by bombarding cities and towns.
Mr Zelensky, speaking late Tuesday in his nightly video address to his nation, accused Russian forces of blocking the aid convoy despite agreeing to the route ahead of time.
"We are trying to organize stable humanitarian corridors for Mariupol residents, but almost all of our attempts, unfortunately, are foiled by the Russian occupiers, by shelling or deliberate terror," he said.
The Red Cross confirmed a humanitarian aid convoy trying to reach the city had not been able to enter.
The convoy's attempt to deliver assistance came as Russian navy vessels joined in what have been weeks of Russian air and land strikes into Mariupol, US officials said.
A senior US defense official, speaking to AP on condition of anonymity to give the Pentagon's assessment, said Russian ships in the Sea of Azov added to the shelling of Mariupol. The official said there were about seven Russian ships in that area, including a minesweeper and a couple of landing vessels.
The hands of one exhausted Mariupol survivor shook as she arrived by train in the western city of Lviv.
"There's no connection with the world. We couldn't ask for help," said Julia Krytska, who was helped by volunteers to make it out with her husband and son. "People don't even have water there."
US President Joe Biden is due to head to Europe for an emergency Nato summit on Thursday on Russia's invasion and increasingly hostile stance toward the West.
Mr Biden is traveling to Brussels and Poland, which has received more than 2 million Ukrainian refugees since the February 24 invasion. He is expected to seek continued unity among Western allies and to announce more sanctions in a punishing series of economic and financial penalties on Russia.
Russian forces ‘in retreat’ in some areas
A Western official, speaking on condition of anonymity to discuss military assessments, said Ukrainian resistance has brought much of Russia's advance to a halt but has not sent Moscow's forces into retreat.
"We have seen indications that the Ukrainians are going a bit more on the offensive now," Pentagon spokesman John Kirby told reporters separately in Washington. He said that was particularly true in southern Ukraine, including near Kherson, where "they have tried to regain territory."
Russia's far stronger, bigger military has many Western military experts warning against overconfidence in Ukraine's long-term odds. Russia's practice in past wars in Chechnya and Syria has been to grind down resistance with strikes that flattened cities, killed countless civilians and sent millions fleeing.
But Russian forces appeared unprepared and have often performed badly against Ukrainian resistance.
The US estimates Russia has lost a bit more than 10 percent of the overall combat capability it had at the start of the fight, including troops, tanks and other materiel.
Western officials say Russian forces are facing serious shortages of food, fuel and cold weather gear, leaving some soldiers suffering from frostbite.
The invasion has driven more than 10 million people from their homes, almost a quarter of Ukraine's population, according to the United Nations.
Thousands of civilians are believed to have died. Estimates of Russian military casualties vary widely, but even conservative figures by Western officials are in the low thousands.
Putin's troops are facing unexpectedly tough resistance that has left the bulk of Moscow's ground forces miles from the center of Kyiv, and they are making slow progress on apparent efforts to cut off fighters in eastern Ukraine. The Russians increasingly are concentrating their air power and artillery on Ukraine's cities and civilians.
Talks to end the fighting have continued by video. Mr Zelensky said negotiations with Russia are going "step by step, but they are going forward."
