Ukraine’s cities stood under relentless Russian fire as NATO leaders met in Brussels and President Volodymyr Zelenskyy called for the alliance to provide unlimited aid to balance the battle against Moscow.

As Western leaders worried about Russia using chemical, biological, or even nuclear weapons, Zelenskyy charged that on Thursday morning, Russia used phosphorous bombs on civilians and added to the uncounted death toll. The Group of Seven leaders are restricting the Russian Central Bank’s use of gold, while the U.S. announced a new round of sanctions on more than 400 Russian elites.

Four weeks into the deadly Russian onslaught, its forces appear to have stalled in many places in the face of fiercer-than-expected Ukrainian resistance. That’s provided the West’s NATO allies time to meet in Brussels on how to make Russia’s offensive as painful as possible for President Vladimir Putin — without triggering a nuclear war.

Here are some key things to know about the Russia-Ukraine conflict:

WHAT’S HAPPENING AS THE WAR GRINDS INTO A SECOND MONTH?

Zelenskyy is calling on people worldwide to gather in public Thursday to show support for his embattled country as he prepared to address U.S. President Joe Biden and other NATO leaders gathered in Brussels.

“Come to your squares, your streets. Make yourselves visible and heard,” Zelenskyy said in English during an emotional video address recorded in the dark near the presidential offices in Kyiv. “Say that people matter. Freedom matters. Peace matters. Ukraine matters.”

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WHAT’S HAPPENING AT THE NATO SUMMIT?

Zelensky insisted in his video address that Western leaders give Ukraine unlimited help against Russia, which is “without limits using its entire arsenal” against the country.

A tiny percentage of the warplanes and tanks controlled by NATO members, he said, could make the difference.

“We can’t just buy those,” Zelenskyy said. “When we will have all this, it will give us, just like you, 100% security.”

Ukraine is also in dire need of multiple launch rocket systems, anti-ship weapons, and air defense systems, Zelenskyy said. “Is it possible to survive in such a war without this?”

To some listening, Zelenskyy’s speech was notable for what he did not say. A senior Biden administration official said that Zelenskyy did not reiterate his request for a no-fly zone — or ask to join NATO.

U.S. officials and Western allies have rejected his previous requests, saying it would lead to direct conflict between NATO and Russia, which Biden has described as a potential World War III.

The administration official requested anonymity to discuss the closed meeting.

— Associated Press writer Christopher Megerian contributed reporting from Brussels.

HOW IS THE WEST CRACKING DOWN ON RUSSIA?

Western nations continued to crank up the cost of war for Putin.

Even as the Russian stock market opened to limited trading Thursday, the G7 leaders announced that they are restricting the Russian Central Bank’s use of gold.

The U.S., meanwhile, announced a new round of sanctions targeting more than 400 elites and members of the Russian State Duma. The efforts, the White House said, were aimed at blunting Russia’s ability to use its international reserves to prop up the economy and fund the war.

The Biden administration’s new sanctions target 48 state-owned defense companies, 328 members of the Duma, Russia’s lower parliament, and dozens of Russian elites. The Duma as an entity was also named in the new sanctions.

Britain on Thursday sanctioned 65 more companies and individuals over Russia’s invasion of Ukraine. The targets include Russia’s largest private bank and a woman the British government said was the stepdaughter of Foreign Minister Sergey Lavrov.

WHAT ARE UKRAINE AND RUSSIA SAYING?

When Russia unleashed its invasion — Europe’s biggest offensive since World War II — on Feb. 24, it seemed likely to swiftly topple Ukraine’s government. But a month into the fighting, the massive country that sprawls across 11 time zones is bogged down in a grinding military campaign of attrition.

Despite evidence to the contrary, Kremlin spokesman Dmitry Peskov insisted the military operation is going “strictly in accordance” with plans.

In its last update, Russia said on March 2 that nearly 500 soldiers had been killed and almost 1,600 wounded. NATO estimates, however, that between 7,000 to 15,000 Russian troops have been killed — the latter figure about what Russia lost in a decade of fighting in Afghanistan.

A senior NATO military official said the alliance’s estimate was based on information from Ukrainian authorities, what Russia has released — intentionally or not — and intelligence gathered from open sources. The official spoke on the condition of anonymity under ground rules set by NATO.

Ukraine, which has released little information about its military losses, also claims to have killed six Russian generals. Russia acknowledges just one dead general.

Wednesday’s shelling of Kyiv claimed the life of another journalist. Oksana Baulina, a Russian reporter for the independent Russian news outlet The Insider, was killed in a Kyiv neighborhood.

WHAT ABOUT WAR CRIMES?

Secretary of State Antony Blinken said the U.S. has made the formal determination that Russia has committed war crimes in Ukraine.

Blinken said there have been numerous credible reports of indiscriminate attacks and attacks deliberately targeting civilians. He said Russian forces have destroyed apartment buildings, schools, hospitals, shopping centers, and ambulances “leaving thousands of innocent civilians killed or wounded.”

Blinken said the U.S. would work with others to prosecute offenders. The International Criminal Court at The Hague is already investigating.

Biden has described the possibility that Russia could use chemical weapons in Ukraine as a “real threat” and said it’s an issue that world leaders will discuss at the NATO summit.

WHAT ARE UKRAINIAN REFUGEES SAYING?

Some of the more than 3.5 million people who have fled Ukraine have shared nightmarish stories of death, destruction, and the painful separation from loved ones.

Natalia Savchenko, 37, arrived in Medyka, Poland, on Wednesday and said the situation in the eastern city of Kharkiv is “terrible.” She said there is no electricity or water, and children are not being given medicine or food.

“People are being killed day and night. They are shooting with everything they have,” she said.