UN Secretary-General Ban Ki- moon Friday reiterated his "grave concern" over the deteriorating situation in east and south Ukraine.
The UN chief also stressed that a "diplomatic solution was the only way out of this crisis."
Ban made the remarks in a statement after Ukraine launched a military operation Friday against the eastern city of Slaviansk, which had been reportedly seized by pro-Russia forces, Xinhua reported.
"Escalating violence and reported further loss of life in the city...is a stark reminder of how dangerous the situation has become," he said in the statement.
"Expansion of militia activities and ongoing seizures of public buildings by unidentified armed groups undercut the letter and spirit of the April 17 Geneva statement."
Ban noted that a diplomatic solution was the only way out of this crisis and that all sides must redouble their efforts to revive the spirit of compromise displayed during the 17 April Geneva talks, the statement said.