(Adds background, context)
TUNIS, Oct 6 (Reuters) - Tunisians began voting on Sunday for a parliament that must address chronic economic problems at a moment when political newcomers are mounting a challenge to the established parties.
Voters queued outside polling stations in the capital Tunis, only eight years after rising up to throw off autocratic rule and introduce democracy in a revolution that inspired the "Arab Spring".
But the failure of repeated coalition governments that grouped the old secular elite and the long-banned moderate Islamist Ennahda party to address a weak economy and declining public services has disillusioned many voters.
Sunday's vote for parliament is sandwiched between two rounds of a presidential election in which turnout has been low and which advanced two political newcomers to the runoff at the expense of major-party candidates.
It is not clear what that may mean for Sunday's election, in which Ennahda is one of several parties hoping to emerge with most votes, including the Heart of Tunisia party of media mogul Nabil Karoui.
While the president directly controls foreign and defence policy, the largest party in parliament nominates the prime minister, who forms a government focused on most domestic policy.
(Reporting By Tarek Amara and Angus McDowall. Editing by Jane Merriman)