Ukrainian President Petro Poroshenko says Russian opposition politician and Kremlin critic Boris Nemtsov was killed because he was going to reveal evidence of Moscow's involvement in the separatist conflict in eastern Ukraine.
Poroshenko said in televised comments on February 28 that Nemtsov told Poroshenko a few weeks ago that he was going to reveal proof of the involvement of the Russian military in the Ukraine crisis.
Poroshenko said "someone was very afraid" of him making the information public and so "they killed him."
Nemtsov -- a major critic of Russian President Vladimir Putin who he accused of orchestrating the conflict in Ukraine -- was shot dead late on February 27 as he walked with a friend across a bridge near the Kremlin.
Putin, who has denied Russia is involved in the fighting in Ukraine, has pledged to find Nemtsov's killers and bring them to justice.
Poroshenko called Nemtsov a friend of Ukraine and a Russian patriot.