Armenia has accused Azerbaijan of attacking civilian areas in a push for the key, Armenian-held town of Shushi in the disputed Nagorno-Karabakh region.
Armenia and neighbouring Azerbaijan have been engaged in intense fighting for more than a month as Azerbaijan's military advances into the disputed, Armenian-held region.
The region has been controlled by Christian Armenian troops for more than a quarter-century but is considered by the United Nations as part of predominantly Muslim Azerbaijan.
Azerbaijan's forces "resumed attacking towns and cities at dawn, targeting the civilian population and the civilian infrastructure," Armenian state news agency Armenpress reported on Thursday.
"The towns of Martuni and Shushi have come under intense Azerbaijani shelling," the report said. Armenia has described Shushi as a crucial strategic point for control over the mountainous region.
Azerbaijan promptly denied attacking civilian areas and in turn accused Armenia of attacking residential areas in the Goranboy and Tartar districts, relatively near the disputed region.
Armenia's military reported that the previous night was "relatively tense in all the directions of the front line," according to a statement by spokesperson Shushan Stepanyan.
Tens of thousands of civilians have been displaced by the flare-up in fighting, which began in late September, the United Nations said in a statement earlier this week, citing assessments from both sides.
With more than 1000 people reported killed, the recent fighting has been the deadliest since Armenia and Azerbaijan fought a war in the late 1980s and early 1990s as they transitioned into independent countries amid the Soviet dissolution.