A missile strike levelled a row of homes in Azerbaijan's second city of Ganja on Saturday, killing 12 and injuring more than 40 people in their sleep in a sharp escalation of the conflict over the disputed Nagorno-Karabakh region.

The early hours attack, which saw a second missile strike another part of Ganja and a third reach the nearby strategic city of Mingecevir, came hours after Azerbaijani forces shelled the ethnic Armenian separatist region's capital Stepanakert.

Armenian and Azerbaijani forces engaged in new fighting on Tuesday over the Nagorno-Karabakh region despite pleas to observe a ceasefire, as the Red Cross warned hundreds of thousands were already affected by the conflict.

A ceasefire between Armenia and Azerbaijan over the disputed Nagorno-Karabakh region was failing to hold Monday as the two Caucasus rivals exchanged new fire while international mediators were to relaunch efforts for a sustained truce.

Armenia and Azerbaijan were moving "towards a truce" to end fighting over Nagorno-Karabakh, the French presidency told AFP, with a deal expected late Friday or on Saturday.

Fighting between Armenian and Azerbaijani forces over the disputed Nagorno-Karabakh region spilled over into Thursday, with fresh shelling in the province's capital ahead of a first meeting of international mediators in Geneva.

Battles raged between Armenian and Azerbaijani forces over the disputed Nagorno-Karabakh region on Tuesday, with both sides vowing to pursue the conflict despite increasing international pressure for a ceasefire. 

Armenian and Azerbaijani forces have intensified their shelling as French President Emmanuel Macron said jihadist militants had been deployed to Nagorny Karabakh in a "serious" new development.

Armenia's leader claimed Friday to have evidence that Azerbaijani forces currently battling Yerevan's troops in the Nagorny Karabakh region are being militarily supported by Turkey.

Armenia and Azerbaijan, two ex-Soviet republics in the Caucasus, are locked in a decades-long territorial dispute with deadly fighting erupting Sunday.

At least 24 people have died after deadly clashes between arch foes Armenia and Azerbaijan, as the latest violence in the decades-long territorial dispute sparked international calls Sunday to halt the fighting.