Russian President Vladimir Putin and Austrian Chancellor Karl Nehammer started negotiations Monday in the Russian presidential residence, Russia's semi-official Interfax reported, citing Kremlin spokesperson Dmitry Peskov.

This marked the first visit to Russia by an EU leader since the invasion started.

After the meeting Nehammer told reporters this wasn't a "friendly visit" with Putin and that he addressed the "serious war crimes in Bucha," The Austrian Press Agency reported. Nehammer said he told the Russian leader that the sanctions will escalate if Ukrainians keep dying, according to The Austrian Press Agency.

At a virtual meeting on Monday, President Joe Biden and Indian Prime Minister Narendra Modi spoke about Russia's war in Ukraine -- a topic that has caused some friction between the two countries as India has taken a more neutral stance.

Biden said, "I want to welcome India's humanitarian support from people in Ukraine, who are suffering a horrific assault, including a tragic shelling in a train station last week that killed dozens of innocent children and women and civilians attempting to flee the violence. The United States and India are going to continue our close consultation on how to manage the destabilizing effects of this Russian war."

Biden added, "I'm looking forward to our discussion today, Mr. Prime Minister. Our continued consultation and dialogue are key to ensuring the US-India relationship continues to grow deeper and stronger, delivering our people and our global good -- good that we all are seeking to manage particularly in your part of the world."

Modi said the situation in Ukraine was "very worrying," noting he has spoken to both Russian President Vladimir Putin and Ukrainian President Volodymyr Zelenskyy and called for peace and direct talks between the two.

Modi called the killings of civilians in the Ukrainian city of Bucha "very worrying." "We instantly condemned the killings and have called for an independent inquiry. We hope that the ongoing discussions between Russia and Ukraine will lead to peace," Modi said via a translator.

"We have also emphasized the importance of the security of civilians in Ukraine and the unhindered supply of humanitarian assistance to them," he added. "We have sent medicines and other relief material to Ukraine and to its neighboring countries. And on Ukraine's request, we will be sending them another consignment of medicines very soon."

After the leaders' call, a senior administration official told reporters that "there was no sort of concrete ask and concrete answer" on India's response to the war in Ukraine.

Asked about India's purchase of Russian oil during the conflict, the official said energy was brought up on the call but that the U.S. "hasn't asked India to do anything in particular."

"We know not all countries will be able to do what we've done" to ban Russian energy imports, the official said. "Other countries have to make their own choices."

"That said, we don't think India should accelerate or increase the import of Russian energy," the official said.

Asked about India's abstention from the United Nations General Assembly vote to suspend Russia from the U.N. Human Rights Council, the official said, "India is going to make its own judgements."

The official also suggested that India can play a role in mitigating the threat the war has posed to the global food supply, and that there was discussion "about what more India might be able to do."

-ABC News' Molly Nagle and Ben Siegel

Vadym Boychenko, the mayor of the hard-hit Ukrainian city of Mariupol, told The Associated Press that more than 10,000 residents have been killed.

Boychenko said, with corpses "carpeted through the streets," it's possible that the southeastern city's death toll is over 20,000.

-ABC News' Mike Trew

The Ukrainian Armed Forces said Monday that Russian troops are continuing to attack hard-hit Mariupol in southeastern Ukraine.

The Ukrainians said the Russians are still partially blocking the northeast city of Kharkiv using rockets, artillery and mortars.

In Kherson, in the south of Ukraine, Russian forces are trying to gain a foothold in the administrative borders, according to the Ukrainians.

And in Severodonetsk in eastern Ukraine, Russian forces made an unsuccessful attempt to storm the city and weren't able to advance deeper into Ukraine's territory, the Ukrainians said.

-ABC News' Irene Hnatiu

Jalina Porter, the State Department's deputy spokesperson, is responding to the Russian attack at a Ukraine train station that killed at least 50, saying, "We can no longer be surprised by the Kremlin's repugnant disregard for human life."

Five children were among those killed when Russian rockets struck the station in Kramatorsk in Donetsk Oblast on Friday morning, according to Ukraine's state-owned railway company. At least 100 people were injured, according to Donetsk Oblast Gov. Pavlo Kyrylenko.

Russia has denied involvement in the attack, which occurred as "thousands" of civilians fleeing the Russian invasion were at the train station waiting to be taken to "safer regions of Ukraine," according to Kyrylenko.

"Civilians are killed when they stay in their homes, and they're killed when they try to leave," Porter said. "Actions like these demonstrate why Russia did not belong on the U.N. Human Rights Council, and they also reinforce the U.S. assessment that members of Russian forces are committing war crimes in Ukraine."

Porter declined to say if the department considers the train station attack a war crime, saying, "Assessing individual criminal liability in specific cases is the responsibility of courts, as well as other investigatory bodies. But as the secretary, Secretary [of State Antony] Blinken, has said, 'Those responsible for war crimes and other atrocities committed in Ukraine will be held to account.'"

-ABC News' Conor Finnegan