A 64 km (40-mile) convoy of Russian tanks and other vehicles was spotted making its way to Ukraine's capital Tuesday as an intense shelling attack targeted the country's second-largest city.
According to American satellite company MAXAR Technologies, the Russian convoy is already less than 50 km (31-miles) from Kyiv.
The satellite company added that additional forces are being deployed in Belarus, less than 32 km (20-miles) north of the Ukraine border, including both ground forces as well as helicopters with air-to-ground assault capabilities.
The White House estimates that in addition to the convoy, a huge "swarm" of Russian forces will invade Ukraine in the coming days, through which Moscow expects to overwhelm the surprisingly stiff Ukrainian resistance.
A British military intelligence update, however, said Russia's advance on Kyiv has made little progress in the past 24 hours due to logistical difficulties and the army has increased its use of artillery north of the capital.
"Russian forces have increased their use of artillery north of Kyiv and in vicinities of Kharkiv and Chernihiv. The use of heavy artillery in densely populated urban areas greatly increases the risk of civilian casualties," said the British Defense Ministry.
"Russia has failed to gain control of the airspace over Ukraine prompting a shift to night operations in an attempt to reduce their losses."
Videos from Kharkiv, Ukraine's second-biggest city, with a population of about 1.5 million, showed residential areas being shelled, with apartment buildings shaken by repeated, powerful blasts.
Authorities in Kharkiv said at least seven people had been killed and dozens injured. They warned that casualties could be far higher.
The country's embattled president, meanwhile, said he believed the stepped-up shelling was designed to force him into concessions.
"I believe Russia is trying to put pressure (on Ukraine) with this simple method," Ukrainian President Volodymyr Zelensky said late Monday in a video address.
He did not offer details of hours-long talks that took place Monday, but he said Kyiv was not prepared to make concessions "when one side is hitting another with rocket artillery."
According to Zelensky, Kyiv remains "a key goal" for the Russians, noting that it was hit by three missile strikes on Monday and that hundreds of saboteurs were roaming the city.
"They want to break our nationhood, that's why the capital is constantly under threat," Zelensky said.
The Russian military has denied targeting residential areas despite abundant evidence of shelling of homes, schools and hospitals.
Ukraine’s ambassador to the U.S. Oksana Markova claimed Monday that the Russian military used widely banned thermo-bombs in its most recent attacks.
"They used a bomb that is actually banned from use under the Geneva Convention... the devastation that Russia is trying to inflict on Ukraine is enormous," the ambassador said.
Amnesty International and Human Rights Watch both affirmed Markova's claims of illegal weapon use by the Russian military.
White House press secretary Jen Psaki did not confirm that Russia had used such weapons, but said that “If it were true, it would potentially be a war crime."
The United States and its allies have imposed sanctions on Russia's central bank, its top businesses, oligarchs and officials, including Russian President Vladimir Putin himself, and barred some Russian banks from the SWIFT international payments system.
The White House estimated that "Russia is facing complete isolation from the world economy." A senior National Security Council official said that "at some point Putin will understand the strategic failure of the invasion of Ukraine."
Moscow, on its part, said on Monday that those supplying lethal weapons to Ukraine will bear responsibility, referring to the weapon shipments several Western countries mobilized to Ukraine - as well as to the recent call by some EU members as well as NATO to continue supplying weapons to Kyiv.
The Russian Foreign Ministry added that the steps the European Union has taken against Russia will not be left without a harsh response.