NATO estimated on Wednesday that between 7,000 and 15,000 Russian soldiers have been killed in four weeks of war in Ukraine, where fierce resistance from the country's defenders has denied Moscow the lightning victory it sought.

Over the course of 10 years, Russia lost 15,000 troops in Afghanistan.

A senior NATO military official said the alliance's estimate was based on information from Ukrainian authorities, what Russia has released, and intelligence gathered from open sources. Under ground rules set by NATO, the official spoke on condition of anonymity.

The West has not given an estimate of Ukrainian military losses, but President Zelenskyy said nearly two weeks ago that 1,300 Ukrainian servicemen had been killed.

The Ukrainian government seemed likely to fall after Russia launched its invasion. Moscow is bogged down in a military campaign with four weeks of fighting left.

Zelenskyy, who has riveted the world's attention with ad hoc videos and speeches to legislatures seeking military aid for his country, is asking for people around the world to gather in public Thursday to show their support.

Come to your streets. Zelenskyy spoke in English during an emotional video address to the nation, recorded in the dark near the presidential offices in Kyiv. Freedom is important. It's important that peace is maintained. Ukraine matters.

Zelenskyy appealed to Russians to leave Russia so as not to give their tax money to the war.

Zelenskyy will speak to NATO members by video on Thursday, and he wants the alliance to provide "effective and unrestricted" support to the country.

With its ground forces slowed or stopped by hit-and-run Ukrainian units armed with Western-supplied weapons, Russian President Vladimir Putin's troops are bombarding targets from afar, falling back on the tactics they used in reducing cities to rubble in Syria and Chechnya.

A senior U.S. defense official said Wednesday that Russian ground forces appear to be digging in and setting up defensive positions outside of the city center as they make little to no progress toward the city center.

The official, who spoke on condition of anonymity to discuss military assessments, said it appears the forces are no longer trying to advance into the city.

The official said that Russian troops appear to be focused on the fight in the Luhansk and Donetsk regions in the Donbas, in order to prevent Ukrainian troops from moving west to defend other cities. The U.S. has seen Russian ships in the Sea of Azov that appear to be trying to send landing ships with supplies, including vehicles, the official said.

A senior Russian official said the country's nuclear arsenal would help deter the West from intervening in Ukraine.

The Russian Federation is capable of destroying any group within minutes at any distance, according to the head of the state corporation. He noted that Moscow has nuclear weapons that are designed for use on battlefields. Missile-building facilities are under the control of Roscosmos.

Russia's military doctrine states that it can use nuclear weapons to force the enemy to back down in a situation when they face imminent defeat. Moscow denied having such plans.

The bluster of Rogozin is well known, but he did not say what actions by the West would be seen as interference. Putin warned that a no-fly zone over Ukraine would cause a conflict with Russia. Western nations said they wouldn't create a no-fly zone.

President Joe Biden warned that Russia could use chemical weapons as he left for Europe to meet with key allies about new sanctions against Moscow.

On the eve of a meeting with Biden, European Union nations signed off on another 500 million euros in military aid for Ukraine.

Zelenskyy appealed to Western countries to stay united in the face of Russia. He said that Ukraine needs tanks and anti-ship systems.

He said that it had been a month of defending ourselves from attempts to destroy us.

Secretary of State Antony Blinken said that the U.S. will work to prosecute Russian troops who have committed war crimes. Evidence of indiscriminate or deliberate attacks against civilians and the destruction of apartment buildings, schools, hospitals, shopping centers and other sites was cited by him.

There are still major Russian objectives that are unfulfilled, including in Kyiv, where the two sides battled for control of multiple suburbs. The war has killed at least 260 people in the capital.

Another journalist was killed by the shelling Wednesday. Oksana Baulina, a Russian journalist, was killed in a neighborhood, according to The Insider.

In the south, the city of Mariupol has seen the worst of the war, enduring weeks of bombardment and street-by-street fighting. Russian attempts to secure a land bridge from Russia to Crimea have been stymied by Ukrainian forces.

The city had 430,000 people before the war, according to Zelenskyy. Desperate attempts to get food and other supplies to those trapped have often failed.

Zelenskyy claimed that Russian forces seized a humanitarian convoy. The Russians were holding captive 11 bus drivers and four rescue workers, according to the deputy prime minister.

Mariupol officials said at least 2,300 people had died, but the true toll is probably much higher. The theater and art school were destroyed by air strikes.

Russian forces bombed and destroyed a bridge in the besieged northern city of Chernihiv, which was used for civilian and aid deliveries.

Kateryna wiped away tears as she spoke about what she had seen. Entire neighborhoods have been destroyed because the city is without gas, electricity or running water.

I don't understand why we have a curse, she said.

The military operation is going in accordance with the plans, despite plenty of evidence to the contrary.

The NATO official said that between 30,000 and 40,000 Russian soldiers have been killed or wounded. Russia said in its last update that almost 500 soldiers had been killed and 1,600 wounded.

The Ukrainians claim to have killed six Russian generals. Russia only acknowledges one dead general.

The first public estimate of Russian casualties since the war began is from NATO. Estimates of Russian or Ukrainian casualties have largely been declined by the U.S. government.

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Anna was reporting from Ukraine. The report was contributed to by Associated Press writers Robert Burns in Washington, Yuras Karmanau in Lviv, and other AP journalists around the world.

We can be reached at letters@time.com.