Armenia and Azerbaijan accused each other on Tuesday of violating a ceasefire in Nagorno-Karabakh, stoking fears of a humanitarian crisis in the enclave.
The Russia-brokered truce buckled despite international calls for the neighbours to strengthen their commitment to it.
Turkey and Armenia swapped recriminations, each blaming the other for making the crisis worse. Nagorno-Karabakh is recognised as part of Azerbaijan but is governed and populated by ethnic Armenians.
On Tuesday, a Reuters cameraman said he watched shelling of the Nagorno-Karabakh town of Martuni, while a television crew from the agency in the Azeri city of Terter said it had been shelled.
The Azerbaijan government accused Armenia of "grossly violating the humanitarian truce" which was agreed on Saturday to allow the sides to swap prisoners and repatriate those killed in the fighting.
Defence Ministry spokesman Vagif Dargiahly said Armenia was shelling the Azeri territories of Goranboy and Aghdam, as well as Terter. Azeri forces were not violating the truce, he added.
Armenian Defence Ministry spokeswoman Shushan Stepanyan denied the accusation. She said Azerbaijan had resumed military operations "supported by active artillery fire in the southern, northern, northeastern and eastern directions".
The fighting, which broke out on September 27, is the worst since a war over Nagorno-Karabakh in 1994 killed about 30,000 people.
The conflict is closely watched abroad because of fears Russia and Turkey could drawn in. Russia has a defence pact with Armenia, while Turkey is allied with Azerbaijan.
Armenian Prime Minister Nikol Pashinyan accused Turkey of muscling its way into the South Caucasus region to further what he called its expansionist ambitions. Turkey denied this.
