15 Armenian soldiers have died in clashes on the country's border with Azerbaijan, Interfax news agency quoted the Armenian parliament as saying on Tuesday.

"There are fatalities and wounded among Armenian troops as a result of fighting that erupted following an attack by Azerbaijani forces," the Armenian defense ministry said Tuesday, adding that the exact number of casualties was being verified and that Yerevan had "lost control of two military positions."

The ministry reported later in the evening that 12 Armenian servicemen were captured by the Azerbaijani military.

"Armenian troops attacked Azerbaijani positions in the districts of Kelbajar and Lachin," an Azeri defense ministry statement said, adding that two Azerbaijani troops were wounded.

The ministry said Azerbaijani troops "stopped the enemy's advance, surrounded, and detained Armenian servicemen."

Baku said Yerevan "is deliberately mounting tensions and is not interested in ensuring peace and security in the region."

According to the defense ministry of Armenia, Azerbaijani forces tried to "breakthrough" the border before being repelled.

As tensions mount between the two nations, the European Union called on both parties to cease hostilities.

"[We] call for urgent de-escalation and full ceasefire," European Council President Charles Michel said on Twitter.

Armenia had appealed to Russia for military support under the Collective Security Treaty Organisation pact, calling for Moscow to help it defend its regional sovereignty in the face of Azerbaijan.

Russia's Interfax news agency reported that Armenian Prime Minister Nikol Pashinyan accused Azerbaijan's troops on Monday of violating the border between the two countries and sacked his Defense Minister.

Pashinyan did not disclose when the incursion took place but told a National Security Council meeting that he fired the Defense Minister over the incident and that senior officials have been discussing it since Sunday.

The rising tensions between Armenia and Azerbaijan - which have been mounting since Sunday in the disputed Nagorno-Karabakh region - are sparking concerns over the ceasefire between the two countries going back to square one after they spent over a year fighting over the region.