Geneva, March 3 (IANS/EFE): UN Assistant Secretary General for Human Rights Ivan Simonovic said on Monday that a possible separatist military offensive against the Ukrainian city of Mariupol would provoke a strong international reaction.

Two weeks after a ceasefire agreement went into effect in eastern Ukraine, Ukrainian governmental forces and pro-Russian separatist troops in Donetsk and Lugansk confirmed that they had completed the withdrawal of their heavy weapons from the agreed separation line.

However, the government in Kiev accused rebels on Sunday of faking the retreat to regroup and prepare a new offensive.

In a press statement given in Geneva coinciding with the release of a UN report concerning human rights in Ukraine, Simonovic warned that an offensive against Mariupol would result in a high number of casualties, as the city is heavily defended.

Simonovic added that there is concern that a crackdown on Mariupol may cause a greater internationalisation of the conflict.

Kiev suspects that the strategic industrial port city of Mariupol, currently under the government's control, might be the new target for separatists.

On February 18, when the ceasefire had already been put into effect, pro-Russian separatists seized control of Debaltseve, a strategic connection point between separatist strongholds in both Donetsk and Lugansk, after intense fighting that ultimately forced the Ukrainian troops to retreat from the city.