In Syria's eastern Aleppo, a rebel-held area, around 275,000 civilians are currently under siege by a Syrian government offensive backed by Russia.
The bombing campaign and continuous airstrikes by the government and its allies "are responsible for the majority of civilian casualties," said Zeid Ra'ad al Hussein, the top United Nations human rights official, in a speech last week.
Zeid Ra'ad al Hussein denounced the bombing campaign, which he said amounts to "crimes of historic proportions."
"What is happening with Russian support in Aleppo is completely inhuman," she said.
British Prime Minister Theresa May had similarly strong words : "It's vital that we work together to continue to put pressure on Russia to stop its appalling atrocities, its sickening atrocities in Syria."
'We are not bombing civilian populations'
Confronted with these charges in an exclusive interview with DW's "Conflict Zone," Alexander Grushko, Russia's NATO ambassador, denied the accusations and said: "We are not bombing civilian populations." He then admitted: "Maybe there is collateral damage."
Asked whether he cares about Russia being accused of committing war crimes in Syria, Grushko said:
"We did everything we could."
Grushko went on to stress that the civilian population in Aleppo is also a victim of terrorist groups like Jabhat Al Nusra and that Russia's main prerogative is to "get rid of the terrible terrorist threat from Syria."
"We help the Syrian army win the war against Daesh," he said, using an alternative name for the so-called "Islamic State" militant group. "Daesh should be defeated."
Are Russia and NATO military competitors?
Since the outbreak of the Ukrainian conflict in 2014 and Moscow's annexation of Crimea, there has been increasing military tensions between NATO and Russia.
NATO has condemned Russia's annexation of Crimea, declaring it illegal and refusing to recognize Moscow's claim over the peninsula.
The United States and the European Union, along with other allied countries, have also responded to the annexation by imposing sanctions on various Russian officials, companies and goods.
In April, Russian jets made several close-range passes at a US Navy ship in the Baltic Sea close to Kaliningrad, inflaming tension.
US Secretary of State John Kerry reacted to the incident by saying: "We condemn this kind of behavior. It is reckless. It is provocative. It is dangerous. And under the rules of engagement that could have been a shoot-down."
In October, Russia started moving nuclear-capable Iskander missiles to Kaliningrad, a Russian enclave in the Baltic Sea and the country's westernmost region. Their close proximity to Lithuania, Latvia, Estonia and Poland have caused a number of officials in Eastern European countries to express alarm over what they see as Russia's provocations.
In response to the growing concerns, NATO is planning its largest military buildup in the Baltic and Poland since the Cold War.
In the interview with Tim Sebastian, Grushko criticized NATO's increased activity in Eastern Europe and said instead of a partnership, Russia and NATO were "engaged in a sort of military competition."
"The United States will station heavy weapons and equipment systems in three West European countries in Germany, Belgium and the Netherlands," he said.
Asked whether he feels sidelined by NATO and the international community, Grushko said:
"Today, there is an attempt to sideline Russia. To isolate Russia. To build a new iron curtain in Europe."
'Situation in Crimea not a result of Russian policy'
Grushko rejected criticism regarding the annexation of Crimea.
"The situation in Crimea was not a result of Russian policy. Full stop," he said, and added that it was the result of a coup in Ukraine.
When Tim Sebastian reminded him that 100 countries rejected the referendum and called it illegal, Grushko said:
"People of Crimea made their choice and that's it. (…) More than 2 million inhabitants of Crimea took Russian citizenship. More than 90 percent supported this integration, returning back to Russia. These are facts."