European Union lawmakers are demanding an international investigation into the killing of Russian opposition politician Boris Nemstov, calling it the "most significant political murder in recent Russian history."

The resolution adopted Thursday also expressed concern that parliamentarians and diplomats were refused entry into Russia to attend Nemtsov's funeral.

Nemtsov, an outspoken critic of President Vladimir Putin, was gathering evidence about Russia's involvement in Ukraine. He was gunned down near the Kremlin on Feb. 27.

The resolution said that Russia is acting "contrary to a functioning democracy" and that government propaganda is turning the nation into a "state of repression, hate speech and fear."