Armenia's Prime Minister Nikol Pashinyan said 49 of its soldiers died in overnight clashes, while Azerbaijan's defence ministry said 50 of its servicemen were also killed.

The neighbouring countries have fought two wars and seen regular smaller clashes span three decades.

On Tuesday, Russia said it brokered a ceasefire for the latest outbreak.

Armenia initially said the fighting had calmed, rather than ended completely. Later, Azerbaijan said it had completed its objectives following "provocations" from its neighbour.

The two countries blame each other for the latest outbreak of violence.

Armenia claimed that several towns along the border had been shelled by its neighbour and that it had responded to the provocation.

Azerbaijan said its infrastructure came under attack first, with military spokesman Lt Col Anar Eyvazov saying that military movements over the past month "demonstrate that Armenia is preparing for a large-scale military provocation".

At the core of the dispute is the region of Nagorno-Karabakh. It is, according to internationally-recognised borders, firmly a part of Azerbaijan - but is populated by ethnic Armenians.

The cultural divide extends beyond politics into religion, too: Armenia is a majority-Christian country, while Azerbaijan is mostly Muslim.