Residents of northwestern Bulgaria are gathering signatures in a petition for a referendum on whether a tunnel should be built under the Petrohan mountain pass.

The step was taken in memory of a writer and researcher Milan Milanov, who dreamed of seeing the now abandoned project come true, but also in view of the foreign investment inflows that infrastructure could bring into the region, daily 24 Chasa quotes Vanina Stoyanova, one of the organizers, as saying.

The Petrohan Pass is part of Pan-European Corridor IV, which connects Dresden in Germany to Thessaloniki and Istanbul and which runs through northwestern Bulgaria, the EU's poorest region.

If the tunnel is opened into the mountains, the stretch between Sofia and Montana, which is part of the corridor, will be shortened by 46 km, campaigners have calculated.

The narrow pass is the shortest route between Sofia and Northwestern Bulgaria.

Over the years there have been several ideas such as widening the road or building a tunnel.

A 24 km section of Republican Road II-81, connecting Sofia with Berkovitsa, Montana and Lom, passes through Petrohan.

The petition initiators have estimated construction price at nearly BGN 70 M, according to 24 Chasa.

The tunnel's length will probably vary between 3.6 km and 9 km.

Referendum campaigners also plan on staging a protest to which President-elect Rumen Radev will be invited to unveil his plans on the future of Bulgaria's north-west, which has faced depopulation, rising unemployment and plummeting standards of living for many years.