Ukraine fears spread of war after blast in eastern city

A member of the Ukrainian armed forces rides an armoured personnel carrier near Artemivsk, eastern Ukraine, February 22, 2015. REUTERS/Gleb Garanich

NIZHNYAYA KRYNKA/KHARKIV, Ukraine (Reuters) - Ukraine said on Sunday it feared unrest could spread beyond territory held by pro-Russian separatists, after an explosion killed two people at a memorial rally in an eastern city far from the front line.

Kiev said it arrested four people who had been armed and trained in Russia after the blast, which killed a policeman and a demonstrator at the rally in Kharkiv, the biggest city in the east, 200 km (125 miles) from the war zone.