“The EU must take action against the political oppression in Russia,” Swedish Foreign Minister Tobias Billström said. “This is particularly important given the fact that on February 16, Alexei Navalny died in Russian captivity.”

The U.K. Foreign Office summoned the country’s Russian ambassador on Friday to “express our outrage at Mr. Navalny’s death,” Leo Docherty, Britain’s Europe minister, told the House of Commons on Monday.

“We made clear that we hold the Russian authorities fully responsible,” Docherty said. Britain will “explore all options” to hold Russian President Vladimir Putin to account, he added.

“No one should doubt the dreadful nature of the Russian system. Years of mistreatment at the hands of the state had a serious effect on Mr. Navalny’s health,” Docherty said.

“His death must be investigated fully and transparently. The Russian authorities must urgently confirm the location of Mr. Navalny’s body to his family, and allow them access to it.”

The Finnish foreign ministry on Monday summoned the Russian ambassador “to emphasize that Russia is responsible and to demand a full and transparent investigation.” The ministry also called for the release of all political prisoners in Russia.