Armenia and Azerbaijan accuse each other of Nagorno-Karabakh truce breach

• The ceasefire began at midnight local time (4 p.m. ET) Saturday, hours after the two countries accused each other of violating a week-old, Russian-brokered humanitarian truce, which was intended to allow the two sides to exchange prisoners and recover bodies.

The big picture: Hundreds of soldiers and dozens of civilians have been killed since the recent fighting began in late September.

• The recent violence is the worst the region has seen in years, and began with coordinated air and missile attacks late last month from Azerbaijan, which claimed Armenian forces had been preparing an attack (Armenia denies that).

The backstory: Nagorno-Karabakh is a mountainous region of around 150,000 people that is populated mainly by ethnic Armenians but lies within the borders of Azerbaijan.

• The countries have both claimed the territory since the collapse of the Soviet Union, fought a war over it from 1992-1994, and stood on the precipice of further conflict since.
• Previous skirmishes, though numerous, have left the stalemate largely unaltered. So has a peace process overseen by the U.S., France and Russia.

Go deeper: Armenian Americans rally in U.S. as Nagorno-Karabakh truce frays

Editor's note: This article has been updated with the spokesperson's comments.