Armenia Leader Threatens Azerbaijan with 'Preventive Strike'

Armenian President Serzh Sarkisian on Monday threatened arch-foe Azerbaijan with an "asymmetrical" response to any attempt to use military means in resolving their long-standing conflict over the disputed Nagorny Karabakh region.

"Until now we were reacting symmetrically ... from now on we could take asymmetrical actions," Sarkisian told a televised meeting with Armenia's defense ministry.

"Hotheads (in Azerbaijan) should expect various surprises. In the event of a major and menacing (military) concentration on our border or along the (Karabakh) frontline, we reserve the right of a preventive strike," he added.

"We are obliged to be merciless towards those who prepare trouble for us."

Azerbaijan is locked in a decades-long conflict with Armenia over Karabakh, an ethnic Armenian enclave in Azerbaijan.

Clashes between Azerbaijani and Armenian forces intensified in January following an unprecedented spiral of violence last year.

Four Armenian soldiers were reported killed this month in fighting on the Armenian-Azerbaijani border and along the Karabakh frontline.

Ethnic Armenian separatists backed by Yerevan seized control of Karabakh during a 1990s war that left some 30,000 dead.

Despite years of negotiations, the two sides have not yet signed a final peace deal, with Karabakh internationally recognized as part of Azerbaijan.

Baku, whose military spending exceeds Armenia's entire state budget, has threatened to take back the region by force if negotiations fail to yield results. 

Armenia, which is heavily armed by Russia, says it could crush any offensive.