MOSCOW (Reuters) - Bidzina Ivanishvili, the head of Georgia’s ruling party and its richest citizen, said on Monday he was quitting politics, two months after a parliamentary election his opponents allege was rigged. Ivanishvili, 64, and his allies in the ruling Georgian Dream party, which won the Oct. 31 election, deny rigging it. International observers said the vote, which triggered street protests, was broadly free and fair. Ivanishvili, who lives in a glass and steel mansion that looms over the Georgian capital Tbilisi, announced his political exit in a letter published on his party’s social media feeds, citing his age and the party’s success in establishing itself as a dominant force. “I have decided to finally quit politics and to step away completely from its management. I leave the post of party chairman, as well as the party itself and am returning to normal life as it was before 2011,” he said. Ivanishvili’s exit could help defuse political tensions in the small South Caucasus country, which is criss-crossed by oil and gas pipelines. He has long been one of the main targets for the opposition’s campaigns. He served as prime minister in 2012-13, but opponents accused him of running the country of 3.7 million from behind the scenes after he stepped down from that position. Ivanishvili, who made much of the $4.8bn Forbes estimates he is worth in Russia in metals and banking in the 1990s, has also been accused by opponents of being close to the Kremlin, something he denies. Russian troops are garrisoned in two breakaway Georgian regions representing one-fifth of the country’s territory, and alleged links to Moscow can be politically damaging in Georgia. Ivanishvili founded the Georgian Dream party in 2012 and a coalition it was part of won control of parliament that same year, defeating the party of former president Mikheil Saakashvili, leader of the 2003 Rose Revolution. It strengthened its grip on power at Oct. 31 parliamentary elections last year, winning 48.23% of the vote, and formed a government. The opposition accused Georgian Dream and its supporters of vote buying, of making threats against voters and observers, and of violations during the count, allegations the party denied.