There have been monumental efforts, especially by Poland, to get weapons into Ukraine and to the front lines.

But a senior official told ABC News there are indications Russia may attack one of those supply chains in Poland before it gets to Ukraine, potentially using air power.

Russian forces have created heavily fortified areas from which to launch long-range artillery, the official said, meaning they can shell cities from a distance rather than send troops into them. Ukrainian President Volodymyr Zelenskyy has repeatedly requested air power assistance in order to destroy these fortified areas.

Ukrainians have seen success in attacking Russian resupply areas, mostly in the north but also among smaller, moving groups.

-ABC News' Martha Raddatz

Ukrainian President Volodymyr Zelenskyy has filmed himself from the street just outside his office, but for the first time since the invasion began, he posted a video message from inside.

“We’re not scared, because you’re not scared,” he told Ukrainians who have taken up arms and told Russia it is not welcome.

“So, I stay here at Bankova Street,” Zelenskyy said. “I’m not hiding from anyone and not afraid of anyone as long as it takes to win in this war, our truly patriotic war.”

The latest address was filmed as a selfie in which he showed a view of Kyiv on Monday night.

“This is Kyiv at night outside the window. This is our office. Monday night. You know, we’re used to saying Monday is a hard day,” he said. “But the country is at war now, so every day is Monday.”

-ABC News’ Christine Theodorou

Ukraine’s national nuclear regulator told the International Atomic Energy Agency on Monday that a new nuclear research facility producing radioisotopes for medical and industrial applications had been damaged by shelling in the city of Kharkiv on Sunday.

The incident did not cause any increase in radiation levels at the site.

The nuclear material in the facility is always subcritical, the IAEA said, and the inventory of radioactive material is very low, so the damage reported would not have any radiological consequence.

Eight of Ukraine’s 15 reactors are currently operating, the IAEA said, citing Ukraine’s nuclear regulator.

IAEA Director General Grossi noted there have been several episodes compromising safety at Ukraine’s nuclear sites, including a recent fire at the Zaporizhzhya Nuclear Power Plant, where two reactors are still operational.

-ABC News’ Christine Theodorou

Ukraine and Russia’s foreign ministers have agreed to meet on the sidelines of a diplomatic forum in Turkey on Thursday in what will be the highest level direct meeting between the two sides since Russia’s invasion.

The meeting was agreed following a call between Turkish President Recep Tayyip Erdogan and Russian President Vladimir Putin on Sunday.

Russia’s foreign ministry spokesperson Maria Zakharova earlier confirmed the two had agreed to a meeting. Ukraine’s foreign minister Dmytro Kuleba has also confirmed it.

It’s not clear that there is much the two will be able to agree on, but it still signals a readiness by Russia to talk. For now, Russia is continuing to put forward hardline demands that Ukraine guarantee it will never join NATO or the European Union.

-ABC News’ Patrick Reevell

While Poland has been welcoming refugees fleeing the destruction in Ukraine, the country will eventually meet its limit on how many people it can take in, Konrad Fijolek, president of Rzeszow, Poland, a city about 60 miles from the Ukrainian border, told ABC News.

Like many cities that border Ukraine, Rzeszow, a town of about 180,000 people, has become a pathway to safety and a lifeline for millions of refugees flooding across the border from Ukraine.

Poland will be able to receive about 1.5 million people, but any more will put the country under strain, Fijolek said.

"If a million or more come, we won't be able to cope," he said.

Some estimates suggest as many as 4 million people could leave Ukraine due to the conflict, but most of the major cities in the country are already full — and officials are attempting to move refugees into smaller cities, a feat that is "not easy," Fijolek said.

So far, all the shelters set up in Poland are temporary, he added.

"We would like to avoid the view of refugee camps here," he said. "We would like people who are escaping from the war to think that what awaits here is proper camp not camps."

In addition, the mental state among the people in Poland is continuing to deteriorate, Fijolek said.

"We as local leaders would like to send the message that if there's any possible action to stop the war [find it] and then try to negotiate, because every day at the border we can see the human tragedy," he said.

-ABC News' Chris Donato and Marcus Moore