NATO is “very closely” monitoring the “increased” influence of Russia in the Western Balkans, alliance Secretary General Jens Stoltenberg warned Wednesday.

He said NATO had seen “several reports about increased Russian influence” in the region, specifically “about Russian intervention in the political process in Montenegro” ahead of its general election in October last year.

“Of course, this is something we are following very closely,” Stoltenberg told reporters during a visit to the Bosnian capital Sarajevo.

Montenegro’s police arrested a group of Serbians on the eve of its October 16 vote and accused them of plotting to seize parliament.

Two Russians are wanted for their alleged involvement, and Montenegro’s former premier Milo Djukanovic has accused his pro-Russian opposition rivals of being behind the plot, which he said included plans for his assassination.

Stoltenberg said NATO was working with partners in the region to “improve and strengthen their intelligence services”.

In the Balkan region, Croatia, Romania, Bulgaria, Greece and Albania are already in NATO while Montenegro is on the brink of joining, with its accession ratified by most of the alliance’s 28 members.

Bosnia is a candidate for membership, and Stoltenberg praised the country’s “strong commitment” to reforming its defence and security sector, although he called for “even more courageous reforms”.

He also said the alliance would “do whatever we can to try to keep tensions down, to avoid any escalation” in the region.