Ecuadorian President Rafael Correa won Sunday's presidential election with 56.8 per cent of the votes, according to the first official results released by electoral authorities, DPA reported.
Electoral Council president Domingo Paredes stressed that "it is impossible" for the trend to change in what remained of the count.
If final official results confirm these figures, Correa - who had long seemed likely to be re-elected in just one round of voting - will be inaugurated for a further four-year term in May and the run-off scheduled for April 7 will not be necessary.
Ecuadorian laws grant a candidate the presidency if he gets over half the votes, or at least 40 per cent of the vote with a lead of 10 percentage points or more over the second-placed finisher.
The left-wing populist Correa proclaimed his victory ahead of the release of any official results.
"This victory belongs to you," Correa told hundreds supporters gathered before the government palace in Quito.
"We have never failed you and we will never fail you: it's nothing for us, all for you. Long live the homeland!" he said.
Standing alongside his mother, his wife and two of his children, Correa made a call for conciliation "to look ahead together to the radiant future that Ecuador has."
Later, at a press conference, he stressed that the "citizens revolution" he is leading must be "irreversible."
Shortly after polling stations closed, exit polls confirmed a resounding victor for Correa. The polling firm Cedatos gave him 58.8 per cent of the votes to Lasso's 20 per cent.
Polling stations opened at 7 am (1200 GMT) and closed 10 hours later. Some 11.6 million people were registered to vote in the Andean country of 15 million, where voting is compulsory for those aged 18-65.
More than 30,000 military and 20,000 police officers were on hand to keep the peace on election day, although only a few minor incidents were reported. Electoral authorities said at the end of voting that the election took place "in peace."
Around 320 international observers from the Organization of American States, the United States, Russia and India were following the poll. Maria Emma Mejia, head of the observers mission of the Union of South American States (Unasur), stressed the "complete normality" of the voting process in the early hours.
Correa, a close ally of Venezuelan President Hugo Chavez, has made international headlines of late, with his crackdown on traditional media and above all by granting asylum to WikiLeaks founder Julian Assange.
Assange has been holed up since June in the Ecuadorian embassy in London. Britain refuses to allow the controversial Assange a safe passage out of its territory, since he is wanted for questioning in Sweden in connection with allegations of sexual assault.
An expert economist, Correa has governed Ecuador since early 2007. The country had five presidents in the 10 years before he took office and Correa has brought political stability with the self-proclaimed goals of fighting poverty and increasing political participation.
Last year, heavy penalties were imposed on three publishers and a journalist of the daily El Universo for having called Correa a "dictator." The Supreme court sentenced each of the men to three years in jail and set fines at 40 million dollars, provoking international outrage - although Correa later dropped executing the judgement.
Correa referred to the media after his win Sunday and asked them to behave responsibly and honestly.
"Never with prior censorship, but definitely with accountability," he said.
If re-elected, Correa has vowed to implement agrarian reform and to turn Ecuador into one of the world's cleanest countries when it comes to energy. The so-called ITT initiative is key in this effort, and Ecuador is prepared to give up exploitation of three oil fields in the Yasuni natural park if the international community gives it half the expected proceeds of 7.2 billion dollars.
Ecuadorians were also to elect Sunday all 137 members of the National Assembly and five representatives for the Andean Parliament.