Ukraine peace 'threatened' by rebel actions: Poroshenko

Ukrainian President Petro Poroshenko speaks during a press conference at the EU Headquarters in Brussels on February 12, 2015 (AFP Photo/Alain Jocard)

Kiev (AFP) - The peace process in Ukraine is being "threatened" by pro-Russian separatists who have virtually encircled Ukrainian troops in the key battleground town of Debaltseve, President Petro Poroshenko said early Sunday, shortly after the start of an agreed ceasefire.

"Unfortunately, the peace process is threatened, the rebels will use Debaltseve to undermine the ceasefire," Poroshenko said during a meeting with the army chief of staff broadcast live on television, after ordering the military to implement the ceasefire from midnight (2200 GMT Saturday).

"As supreme commander of the armed forces, I want peace," Poroshenko added.

A surge in fighting around the strategic railway hub of Debaltseve in the hours before the ceasefire has cast doubt on whether the truce will be respected.

The fragility of the ceasefire was further highlighted when rebels on Saturday warned that they would consider it an act of aggression if surrounded Kiev forces made any attempts to move out of Debaltseve after the ceasefire's start.

"These attempts will be stopped by us and the enemy will be destroyed," said Donetsk rebel leader Alexander Zakharchenko -- considered by the West to be a Kremlin puppet.

Kiev in turn accused Zakharchenko of essentially announcing that his forces would not respect the ceasefire.

"This is just more proof of the undisguised attempts by Russia and the terrorists it controls to scuttle the agreements for a ceasefire and peaceful resolution," Ukraine's national security council said in a statement.