Boris Nemtsov, the Russian opposition leader, was shot dead near the Kremlin two years ago.
North Korean leader's half brother was killed by a nerve agent in the airport two weeks ago.
In a statement, Hibatullah Akhundzada says more trees are needed "for the beautification of Earth".
Bleak mood in Greece as debt crisis rolls on
Meeting a Soviet-era dissident again after 35 years
Australia moves towards art first, disability second
What it was like growing up intersex in Uganda
Malaise in rural France ahead of presidential vote
Returning to Bolivia's 'tourist prison' 20 years later
Is travel insurance completely pointless?