U.S. Secretary of State Antony Blinken said Kyiv “could well be under siege” in what U.S. officials believe is a brazen attempt by Russian President Vladimir Putin to install his own regime.

Ukrainian President Volodymyr Zelenskyy appealed to global leaders for even more severe sanctions than the ones imposed by Western allies and for defense assistance.

Zelenskyy cut diplomatic ties with Moscow, declared martial law and ordered a full military mobilization that would last 90 days. He said that 137 people, including 10 military officers, had been killed, and one of his advisers said about 400 Russian forces had died. Moscow has given no casualty count. Neither claim could be independently verified.

The conflict has shook global financial markets with stocks plunging and oil prices soaring amid concerns that heating bills and food prices would skyrocket. Condemnation came not only from the U.S. and Europe, but from South Korea, Australia and beyond — and many governments readied new sanctions. Even friendly leaders like Hungary’s Viktor Orban sought to distance themselves from Putin.

President Joe Biden announced new sanctions that will target Russian banks, oligarchs, state-controlled companies and high-tech sectors. He added that the measures were designed not to disrupt global energy markets. Russian oil and natural gas exports are vital energy sources for Europe.

Biden is to meet this morning with fellow leaders of NATO governments in what the White House described as an “extraordinary virtual summit” to discuss Ukraine.

British Prime Minister Boris Johnson said he aimed to cut off Russia from the U.K.’s financial markets as he announced sanctions, freezing the assets of all large Russian banks and planning to bar Russian companies and the Kremlin from raising money on British markets.

Zelenskyy urged the U.S. and West to go further and cut the Russians from the SWIFT system, a key financial network that connects thousands of banks around the world. The White House has been reluctant to do that, worried it could cause enormous economic problems in Europe and elsewhere in the West.

The U.S. and its NATO partners have shown no indication they would send troops into Ukraine, fearing a larger conflict. NATO reinforced its members in Eastern Europe as a precaution, and Biden said the U.S. was deploying additional forces to Germany to bolster NATO.