Venezuela's leftist president, Hugo Chavez, claimed victory on Monday with the support of almost 60 per cent of the votes cast in a weekend referendum on his leadership.

With 94 per cent of the vote counted, National Elections Council president Francisco Carrasquero said nearly 5 million Venezuelans cast ballots indicating Chavez should continue in his job, compared to 3.6 million who wanted him removed from office.

But Carrasquero stopped short of declaring Chavez the winner.

Hugo Chavez addresses the crowd after his win.

Former U.S. President Jiimy Carter, however, who was leading a team of international observers monitoring the recall vote, endorsed Chavez's claim to have won.

"Our findings coincided with the partial returns announced today by the National Elections Council," Carter said.

Carter's announcement appeared to deflate opposition claims of widespread fraud.

Signs of support for Chavez in Caracas (AP photo)

Opposition politicians had been quick to call the results fraudulent.

"We firmly and categorically reject the result," opposition leader Henry Ramos Allup said at a news conference Monday. "We're going to collect the evidence to prove to Venezuela and the world the gigantic fraud which has been committed against the will of the people."

Nevertheless, Chavez supporters set off fireworks in the capital of Caracas to celebrate the populist president's apparent victory.

"It is absolutely impossible that the victory of the 'no' be reversed," Chavez declared in a victory speech from a balcony of his palace.

The size of the "no" vote will allow the 50-year-old former paratrooper to serve out the rest of his six-year term in office, which began in 2000.

This was Venezuela's first-ever attempt to recall a president, and ended a two-year drive by opposition parties to oust Chavez.

He is adored by most of the country's poorer citizens. However, the wealthy say he is ruining the economy of the world's fifth-largest oil exporter by spending oil revenues lavishly to fund social programs, and accuse him of destroying the country's democratic institutions.

A huge voter turnout, with lineups stretching two kilometres in places, led election officials to keep polling stations open an extra eight hours Sunday night. Everyone in line as of the official closing at midnight was allowed to vote.

Many people lined up for seven hours in order to vote.

"This is the largest turnout I have ever seen," said former U.S. President Jimmy Carter, who monitored the vote. "There are thousands of people in line, waiting patiently and without any disturbance."

Problems with electronic voting machines also delayed the process. They were designed to prevent voters from voting more than once by registering people's thumbprints, but even Chavez had to move to another machine to vote because his first attempt failed.