REPUBLIKA.CO.ID, BRUSSEL -- NATO secretary general Anders Fogh Rasmussen on Tuesday condemned Russia's "illegal" annexation of Crimea and urged restraint from both Moscow and Kiev after the death of a Ukrainian soldier.

"Russia has disregarded all calls to step back into line with international law and continues down the dangerous path," Rasmussen said in a statement.

"There can be no justification to continue on this course of action that can only deepen Russia's international isolation," he said.

"Crimea's annexation is illegal and illegitimate and NATO allies will not recognise it."

Earlier Tuesday, President Vladimir Putin signed a treaty claiming the Black Sea region of Crimea as Russian territory as Ukraine warned the showdown had entered a "military stage" after soldiers were killed on both sides.

Rasmussen added that he was "deeply concerned" by reports of the death of a Ukrainian soldier.

"It is urgent that all sides show restraint and take all possible steps to avoid further escalation."

Ikuti Whatsapp Channel Republika