United Nations (UN) Secretary-General Ban Ki-moon is warning that the situation in eastern Ukraine "could quickly spin out of control."
A statement released today by the office of his spokesman says Ban is "deeply concerned" about the continued violence in the region, and it stresses that "military action must be avoided at all costs."
The comments came shortly after Ukrainian forces launched an operation to drive pro-Russia insurgents out of occupied buildings in the region, prompting new threats from Russian President Vladimir Putin.
The operation killed at least two pro-Russia militants. Russia's defence minister has announced new military exercises for troops massed near Ukraine's border.
"The stakes are now so high," the UN statement says.
