UN chief calls for dialogue on Ukraine

UN Secretary General Ban Ki-moon has called on all sides in the Ukraine crisis to "exercise maximum restraint" and engage in dialogue to de-escalate the situation there.

Ban's appeal came as Ukraine accused Moscow of "aggression" after Kalashnikov-wielding gunmen seized two security buildings in its restive eastern rust belt amid spreading protests demanding the Russified region join Kremlin rule.

Ban is "deeply concerned" about the deteriorating situation and "growing potential for violent clashes," a UN statement said.

The secretary general "appeals to all sides to work towards calming the situation, adhere to the rule of law and exercise maximum restraint," the statement added.

He also "calls again for urgent and constructive dialogue to de-escalate the situation and address all differences."