Opposition leader Boris Nemtsov was killed outside the Kremlin last year. Alexander Litvinenko, was killed in London by polonium poisoning in 2006 and journalist Anna Politkovskaya was killed outside her apartment. Lawyer Sergei Magnitsky died in prison. Others working on investigation of corrupt Russian politicians also died suspiciously. Business leaders imprisoned or ousted under Putin are Mikhail Khodorkovsky, head of the oil giant Yukos, and associate Platon Lebedev.