Gun battles between the two leading armed groups in Tripoli killed two people and forced the closure of the Libyan capital's only civilian airport, officials said on Tuesday.Libya has seen more than a decade of stop-start conflict since the 2011 NATO-backed revolt that toppled strongman Moamer Kadhafi, with a myriad of militias forming opposing alliances backed by foreign powers.A period of relative stability had led the United Nations to express hope for delayed elections to take place this year, and the latest fighting triggered international calls for calm.