Ukraine rebels move to encircle government troops in new advance

A rescue worker removes remains of a shell on a street in Mariupol, eastern Ukraine January 25, 2015. REUTERS/Nikolai Ryabchenko

KIEV/ST PETERSBURG (Reuters) - Russian-backed rebels advanced to encircle a Ukrainian army garrison town on Monday in a new offensive that has again unleashed all-out war after a five-month ceasefire and brought threats of new Western sanctions against Moscow.

The United States and the European Union are considering new measures after accusing Russia of openly supporting the latest rebel advance with money, arms and troops on the ground.