The loss of the key town of Debaltseve to Russian-backed separatists, the latest in a string of big battlefield defeats for Ukraine, narrows the options for President Petro Poroshenko in his dealings both with Moscow and with the West.

No sooner did the strategic railway junction fall to the rebels on Wednesday, with thousands of Ukrainian soldiers withdrawing under fire, than separatists re-opened another old front, attacking government positions near Mariupol, a strategic coastal city in the southeast.

The grim message, it seems, was: 'There's more to come. The breakup of Ukraine does not stop here'.