Filippo Grandi, the United Nations High Commissioner for Refugees, said the number of Ukrainians who've fled their country has climbed to 677,000.

Diplomats from Western countries were seen on video walking out in protest as Russian Foreign Minister Sergei Lavrov addressed the U.N. Human Rights Council and Conference on Disarmament.

The meeting was held Tuesday in Geneva and Lavrov gave his address via video.

The Human Rights Council has faced criticism for years for including human rights abusers, including Russia. In a prerecorded video to the council, Secretary of State Antony Blinken questioned whether Russia should be allowed to keep its seat.

"One can reasonably ask whether a U.N. member state that tries to take over another U.N. member state -- while committing horrific human rights abuses and causing massive humanitarian suffering -- should be allowed to remain on this council," he said.

Blinken accused Russia of hitting civilian targets like schools, hospitals, residential buildings, critical infrastructure, and cars, buses, and ambulances -- including the "monstrous rocket strikes" on an apartment complex in Kharkiv.

"Reports of Russia's human rights abuses and violations of international humanitarian law mount by the hour," he said.

"These are the human rights abuses this council was created to stop. If we cannot come together now, when will we come together?" he asked.

-ABC News' Fergal Gallagher, Conor Finnegan

Filippo Grandi, U.N. high commissioner for refugees, told the Security Council Monday there's “a growing number of unaccompanied and separated children" in the unending lines of refugees fleeing Ukraine.

UNICEF said there are "anecdotal reports of heartbreaking stories of fathers -- or families -- arriving at the border with their children and relinquishing them to the border guards, then remaining in Ukraine.”

UNICEF said it doesn't have numbers yet on unaccompanied or separated children.

-ABC News' Zoe Magee

A rocket attack on an administrative building in Kharkiv in northeast Ukraine has killed at least six people and injured another seven, Ukrainian officials said.

An Indian student was among those killed, according to the Indian government.

A senior administration official told ABC News the U.S. has learned that Russia continues to plan for a “devastating” attack on Ukraine, warning that "the Russians … will crush Ukraine."

-ABC News' Martha Raddatz

Secretary of State Antony Blinken closed his remarks to the U.N. Security Council meeting by challenging the Russian Federation to "announce today -- with no qualification of equivocation or deflection -- that Russia will not invade Ukraine, stated clearly stated plainly, to the world."

"And then demonstrate it by sending your troops, your tanks, your planes back to their various can hangars and sending your diplomats to the negotiating table," he added.

Blinken laid out how the U.S. believes Russia will attack Ukraine -- but said he would welcome being wrong and for Russia to withdraw.

"Now, I'm mindful that some have called into question our information, recalling previous instances where intelligence ultimately did not bear out," he said, apparently referring to a similar address then-Secretary of State Colin Powell famously made to the Security Council presenting U.S. intelligence to justify the Iraq War. "But let me be clear, I am here today not to start a war, but to prevent one," he said, citing allies that agree with U.S. assessments.

"If Russia doesn't invade Ukraine, then we will be relieved that Russia changed course and proved our predictions wrong. That would be a far better outcome in the course we're currently on. And we'll gladly accept any criticism that anyone directs at us," Blinken said.

He continued, "Russia can still make if there's any truth to his claim that is committed to diplomacy. Diplomacy is the only responsible way to resolve this crisis"

Blinken also said that he sent a letter to Russia's Foreign Minister Sergei Lavrov earlier Thursday proposing that they meet next week in Europe following their talks in recent weeks "to discuss the steps that we can take to resolve this crisis without conflict" and that U.S. is also proposing meetings at the NATO Russia Council and the OSC Permanent Council.

"These meetings can pave the way for a summit with key leaders in the context of de-escalation to reach understandings on our mutual security concerns," he added.