(Reuters) - The party of East Timor independence hero Xanana Gusmão has won most votes in a parliamentary election, preliminary results in state media showed on Tuesday, boosting his chances of his return as premier and a new phase of opposition rule.

Gusmão's National Congress for Timorese Reconstruction (CNRT) won about 42% of ballots cast with 100% of the votes counted, according to election commission data carried by broadcaster Radio-Televisão Timor Leste.

Reuters could not reach the election commission for confirmation on Tuesday.

The Revolution Front for an Independent Timor-Leste (FRETILIN), the party of Prime Minister José Maria Vasconcelos, popularly known as Taur Matan Ruak, was second with about 26% of the votes, with the rest split among 15 parties.

Sunday's contest was the fifth parliamentary election since East Timor, also known as Timor-Leste, a country of 1.3 million people that gained full independence in 2002 after a quarter-century rule by neighbouring Indonesia.

The former Portuguese colony must now wait to see who will be chosen as prime minister by the newly formed legislature.

The election had been billed as a battle of two former resistance figures, CNRT's Gusmão, 76, and FRETILIN's Mari Alkatiri, 73, with Gusmão seen by analysts as the favourite.

Heavily dependent on its fast-depleting oil reserves for revenue, the half-island nation faces a challenge with poverty and diversifying its economy, which at $3.6 billion is one of Asia's smallest.

The election follows last year's victory in a presidential ballot for independence leader and Nobel laureate José Ramos-Horta, also of the CNRT party.

Gusmão, a former guerrilla leader, was East Timor's first president and served as prime minister from 2007 until his resignation from the post in 2015.

(Reporting by Stanley Widianto in Jakarta; Editing by Martin Petty)