Pro-Russian politician Badra Gunba was declared the winner of the runoff presidential election in the breakaway Georgian region of Abkhazia, officials said Sunday.Abkhazia is recognised by most of the world as Georgian territory but has been under de facto Russian control since a brief 2008 war between Georgia and Russia.Gunba won 54.73% of the vote in the second round, while opposition leader Adgur Ardzinba received 41.54%, Dmitry Marshan, chair of the separatist region's election commission, told reporters.Russian President Vladimir Putin congratulated Gunba, saying the Abkhazian people had expressed their "free popular will."No candidate won a majority in the first round on February 15, forcing a runoff.Abkhazia has been gripped by tension since November, when protesters ousted pro-Kremlin president Aslan Bzhania over a Russian investment bill that critics argued would lead to uncontrolled development in the Black Sea region.Bzhania was the third Abkhazian leader to resign due to protests since 2014.Gunba was vice president and acting leader, while Ardzinba is a former economy minister aligned with the protesters while still backing ties with Russia.Gunba travelled to Moscow for meetings with Russian officials, including top diplomat Sergei Lavrov, days before the first round of voting, in what Ardzinba's camp cast as unfair competition.The second round, held Saturday, was briefly disrupted after masked attackers stormed a polling station in a northwestern town and threatened election officials.Russia's Investigative Committee, which probes major crimes, said Saturday it was investigating "attacks on Russian citizens" during the election.Tbilisi denounced the election as an illegal and blatant violation of its sovereignty.Abkhaz separatists expelled tens of thousands of Georgians from the region during and after a war spurred by the collapse of the Soviet Union in the early 1990s.