Nikolai Glushkov, a Russian businessman who has been living in exile in the U.K., was found dead in his home late Monday night, the Guardian reports. The circumstances of his death are not immediately clear.

Why it matters: Glushkov is an ally of Boris Berezovsky, the late oligarch who was Putin's top foe in the West until his death in 2013. The fact that Glushkov's death comes so soon after the poisoning of Sergei Skripal, and with the U.K. threatening a response, has intensified the scrutiny surrounding it.