Mr Guterres was on around 28 per cent; Mr Ruak 25 per cent; and Mr Ramos-Horta on 18 per cent, with about 73 per cent of the total votes cast counted, Mr Valls said.
Mr Guterres was "happy with the result" so far, his campaign media spokesman Jose said, adding low voter turnout might have affected his overall vote.
"His campaign team is already working on a strategy for the run-off round, which he is confident he will win."
Saturday's vote marked the poor and chronically unstable country's second presidential election as a free nation. It was the first in a series of key events for the country as it enters a pivotal period.
In May, East Timor will celebrate 10 years of independence from Indonesia, and in June, voters will choose a new government in a general election.
At the end of the year the nation of 1.1 million people bids goodbye to UN forces stationed in the country since 1999.