The leaders of Armenia and Azerbaijan have met in Switzerland to discuss their long-running dispute over Nagorno-Karabakh.

The separatist region of Azerbaijan has been under the control of Armenia's military and local ethnic Armenians since an all-out war ended in 1994.

Military clashes between the two sides have escalated in recent days, with Azerbaijan saying three of its troops have been killed.

Switzerland's Foreign Ministry said Armenian President Serzh Sargsyan and Azerbaijan's President Ilham Aliyev met in Bern on Saturday. It provided no details of the meeting.

Switzerland chairs the Organization for Security and Cooperation in Europe (OSCE), which has been working to mediate between the two sides.