Russian President Vladimir Putin has called for an end to the fierce fighting renewed between Armenia and Azerbaijan in the region of Nagorno-Karabakh, where a conflict is threatening to resurface after having remained frozen since 199s4.

Both Armenia and Azerbaijan maintain the other side began the fighting, with conflicting reports about details and casualties.

Russian media outlets report that Russian Defense Minister Sergey Shoigu has already spoken with his counterparts in the two countries.

Nagorno-Karabakh, an Armenian exclave surrounded by the territory of Azerbaijan and also claimed by Baku, has been an arena of renewed fighting since Friday evening.

Interfax agency quotes Putin's spokersperson Dmitry Petkov as saying the President has called on all sides to show restrained in order to prevent further casualties.

The agency also cites data from the Defense Ministry of the so-called Nagorko-Karabakh Republic (recognized only by Armenia and a few entities in the world) suggesting "between 40 and 50 troops of Azerbaijan" have lost hteir lives.

For its part, Azerbaijan estimates the death toll at "more than 100 servicemen of the Armenian armed forces", accordign to Trend News Agency's English-lanage website.

Nagorno-Karabakh is currently under the control of Armenian separatists (ethnic Armenians in the exclave number 146 000) and is backed by the government of Armenia. There have been occasional clashes since a ceasefire was declared in 1994.