Venezuelan opposition leader Henrique Capriles says more than 70,000 people who endorsed a petition for a referendum to oust President Nicolas Maduro validated their signatures on Monday.
Just under 200,000 valid signatures are needed for the process to go ahead.
Mr Maduro was elected in April 2013 and his term runs until 2019.
The opposition blames his socialist policies for rampant inflation and the shortage of food and basic goods.
Mr Capriles said the massive presence of voters on the first day of the validation process was a clear sign that Venezuelans wanted a change of government.
“What we saw today were queues across the country…That’s a warning for Maduro, ,” Mr Capriles said.
Those who endorsed the petition will have until Friday to have their identity cards and fingerprints checked in posts set up by the National Electoral Council (CNE).
The petition had almost two million signatures but election officials said 600,000 of those were fraudulent.
Only 1% of the electorate, or 194,729 voters, however, need to endorse the referendum on this first phase.
According to Mr Capriles, quoting official CNE figures, 71,557 signatures were authenticated on Monday.
The opposition says that under Mr Maduro’s socialist government and that of his predecessor in office, the late Hugo Chavez, the oil-rich country was mismanaged to the point of collapse.
The government says the country’s problems, which include the world’s highest inflation and shortages of basic goods, are due to an economic war being waged by ‘imperialist forces.’
Opposition leaders handed in the petition on 2 May, calling for a recall referendum.
They want the vote to be held this year, as its timing is key for what happens next.
Should the referendum be held before 10 January and go against Mr Maduro, fresh elections will be triggered. But if the vote were to be held after 10 January in the last two years of Mr Maduro’s mandate, he would ‘be replaced by his vice-president and supporter, Aristobulo Isturiz.’
The opposition still has to overcome a number of hurdles before a recall referendum can be held.
If enough signatures on this initial petition are validated, opposition leaders will have to hand in a second petition signed by almost four million people.
Only when the electoral authorities have established that the requirements have been met on that second petition will the recall referendum be held.