Azerbaijan said on Friday that one of its soldiers was wounded when Baku's positions came under fire overnight from Armenian forces, accusations that Armenia denied.

In a statement, the Azerbaijani defense ministry said Armenian forces had fired from several directions at its positions in Nakhchivan, an Azerbaijani enclave separated from the rest of the country by Armenian territory. The wounded soldier was given first aid and taken to a hospital, it said.

Armenia's defense ministry denied Baku's assertion, the TASS news agency reported.

On Thursday, Azerbaijan captured six Armenian servicemen while they were trying to cross the border, the latest twist in a simmering border dispute. The Armenian defense ministry said that the six soldiers were captured "when they carried out engineering work in the protected territory of the military unit of the Armenian Armed Forces in the border section of Gegharkunik region" on the border with Azerbaijan.

"Our servicemen carried out work to equip the border with Azerbaijan, carried out mining work with the installation of warning signs, there was no purpose of sabotage. The incident took place on our territory," Armenian Prime Minister Nikol Pashinian said Thursday, calling for their immediate release. He emphasized, such incidents occur "because some forces want us to get used to the presence of the Azerbaijani military on our territory, but this will not happen."

Pashinian also suggested that international observers from Russia or other Minsk Group countries be deployed to Armenia's border with Azerbaijan and demanded Baku to withdraw its troops from the border, the Interfax news agency reported.

The situation on the border between Armenia and Azerbaijan escalated on May 12 when Yerevan accused Baku of carrying out certain work in order "to clarify the borders" in one of the border areas of the Syunik region. Pashinian informed Russian President Vladimir Putin about his instructions to seek consultations from the Moscow-led Collective Security Treaty Organisation (CSTO) in connection with the situation on the border with Azerbaijan.

Last year the two ex-Soviet countries in the Caucasus region fought for six weeks for control of Nagorno-Karabakh, a region in Azerbaijan that had been occupied by Armenian separatists for decades.

Some 6,000 people were killed in the conflict which ended after Moscow brokered an agreement between Yerevan and Baku that saw Armenia hand to Azerbaijan large sections of the territory it had controlled for decades, including Kalbajar.

The cease-fire, monitored by some 2,000 Russian peacekeepers, has largely held but tensions have persisted and there have been several border incidents.