At least 3,998 civilians have been killed and 4,693 others have been injured in Ukraine since Russian forces invaded on Feb. 24, according to the latest figures from the Office of the United Nations High Commissioner for Human Rights (OHCHR).

At least 260 children were among the dead and 404 among the injured, according to the OHCHR.

"Most of the civilian casualties recorded were caused by the use of explosive weapons with a wide impact area, including shelling from heavy artillery and multiple launch rocket systems, and missile and air strikes," the agency said in a statement Thursday. "OHCHR believes that the actual figures are considerably higher, as the receipt of information from some locations where intense hostilities have been going on has been delayed and many reports are still pending corroboration."

Those areas include Mariupol in the Donetsk Oblast, Izium in the Kharkiv Oblast and Popasna in the Luhansk Oblast, where the OHCHR said "there are allegations of numerous civilian casualties." Casualty numbers from those locations "are being further corroborated" and thus are not included in the latest statistics, according to the agency.

The Russian military's airborne forces, known as the VDV, "have been heavily involved in several notable tactical failures since the start of Russia's invasion" of neighboring Ukraine, according to the U.K. Ministry of Defense.

"This includes the attempted advance on Kyiv via Hostomel Airfield in March, the stalled progress on the Izium axis since April, and the recent failed and costly crossings of the Siverskyi Donets River," the ministry said Thursday in an intelligence update.

"Russian doctrine anticipates assigning the VDV to some of the most demanding operations," the ministry added. "The 45,000-strong VDV is mostly comprised of professional contract soldiers. Its members enjoy elite status and attract additional pay. The VDV has been employed on missions better suited to heavier armoured infantry and has sustained heavy casualties during the campaign."

The VDV's "mixed performance likely reflects a strategic mismanagement of this capability and Russia’s failure to secure air superiority," according to the ministry.

"The misemployment of the VDV in Ukraine highlights how Putin’s significant investment in the armed forces over the last 15 years has resulted in an unbalanced overall force," the ministry said. "The failure to anticipate Ukrainian resistance and the subsequent complacency of Russian commanders has led to significant losses across many of Russia’s more elite units."

Drone footage released by Russian media shows the devastation inside the Azovstal steel plant in Mariupol, Ukraine, where Ukrainian forces fended off Russian troops for weeks amid intense fighting before surrendering.

The drone footage released by the Russian news outlet MIC Izvestia showed the collapsed walls of the plant and twisted metal and debris strewn about the entire facility.

The Russian Defense ministry on Friday said the last Ukrainian fighters defending Azovstal had surrendered, giving Russia full control of the port city of Mariupol.

The seizure of Mariupol, gives Russia command of a land route linking the Crimean Peninsula, which Moscow seized in 2014, with mainland Russia and parts of eastern Ukraine held by pro-Russian separatists.

Canada's Defense Minister Anita Anand announced Tuesday that her country is sending Ukraine more than 20,000 artillery rounds of 155mm NATO-standard ammunition, to further support Ukraine’s military response to Russian leadership’s "illegal, and unjustifiable invasion."

The ammunition, Anand said, has been sourced from the United States at a cost around $98 million and that work is underway to deliver it to Ukraine as quickly as possible.

The ammunition can be fired from M777 howitzer cannons that Canada and its allies have donated to Ukrainian forces.

“Canada stands with Ukraine and its people as they resist Putin’s illegal and unjustifiable assault," Anand said. "Today’s announcement is another example of our unwavering commitment to provide Ukraine with the comprehensive military aid it needs to defend its sovereignty, territorial integrity, and independence."

White House national security advisor Jake Sullivan hinted Thursday of more sanctions coming against Russia in the "next week or two" aimed at targeting ways Moscow is evading sanctions already imposed.

“Where our focus will be over the course of the coming days is on evasion,” Sullivan said Thursday at the Economic Club of Washington. “As Russia tries to adjust to the fact that it’s under this massive economic pressure, what steps do they take to try to evade our sanctions and how do we crack down on that? And I think we'll have some announcements in the next week or two that identify targets that are trying to facilitate that evasion both inside Russia and beyond."

When Sullivan was asked whether sanctions will automatically be lifted if a negotiated peace deal between Russia and Ukraine is worked out, he appeared cautious with his words, saying, “a lot of that depends on what the shape and scope” of the agreement is.

“A lot of it depends on what the Ukrainians, in consultation with us and the Europeans come to agree to," Sullivan said. "You know, we're not going to do a deal over the head of the Ukrainians where we give a bunch of sanctions relief to Russia. But if some measure of sanctions relief were built in to some credible diplomatic solution led by the Ukrainians, that's something that we would happily discuss."

But Sullivan said Russian oligarchs shouldn't expect to ever get back their yachts and other assets seized under sanctions that have been imposed, saying the ultimate goal is "not to give them back” once the war is over.

“The president is actively looking at how we can deal with the fact that as we seize these assets, our goal is not to give them back. Our goal is to put them to a better use than that," Sullivan said. "But I'll be careful in what I say today because there's an ongoing kind of policy process around how we end up dealing with that question. But, rest assured, that the goal is not just to sit on them for a while."

-ABC News' Justin Gomez