Azerbaijan and Armenia are both reporting more losses in a sharp escalation of fighting over the South Caucasus region Nagorno-Karabakh, with 18 soldiers now confirmed dead.

The Azerbaijani region and some adjacent territory have been under the control of Armenian soldiers and ethnic Armenian troops since the 1994 end of a six-year separatist war. Both sides report frequent shootings and attempted incursions along the cease-fire line, but the latest outbreak of fighting is the worst in many years.

Azerbaijan's Defense Ministry said Monday that 13 soldiers were killed in fighting that spiked over the weekend, while Nagorno-Karabakh's armed forces said five of its soldiers were killed.

Armenia's prime minister said the presidents of the two countries would meet at the end of the week in Russia. Azerbaijan hasn't confirmed this.