President of Ukraine Petro Poroshenko leading a session of the national security and defence council  in Kiev. Photograph: Mykhailo Markiv/Ukrainian presidential press service/AFP/Getty Images

Ukraine on Monday imposed martial law for 30 days in parts of the country most vulnerable to an attack from Russia after president Petro Poroshenko wa(...)

Russian jet fighters fly over a bridge connecting the Russian mainland with the Crimean peninsula with a cargo ship beneath it after three Ukrainian navy vessels was stopped by Russia from entering the Sea of Azov via the Kerch Strait in the Black Sea, Crimea. File photograph: Pavlishak Alexey/Reuters

Ukraine accused Russia of illegally seizing three of its ships in the Black Sea after opening fire on them on Sunday, a charge that if confirmed coul(...)