Mozambique's newly-elected president Armando Guebuza has called on the opposition Renamo party to work with him to fight poverty and disease.
Mr Guebuza is Mozambique's president elect
Mozambique is one of the most disadvantaged countries in the world.
Mr Guebuza, the candidate of the governing Frelimo party, said he would use his victory as a real force for change in Mozambique.
He was declared the winner on Tuesday, nearly three weeks after the election, but Renamo are contesting the results.
Frelimo supporters greeted the result with joy when it was announced that Mr Guebuza had taken 64% of the vote.
The former interior minister and wealthy businessman, nicknamed "Mr Gue-business", said the result was a victory for the Mozambican people, AFP news agency reported.
"Only united we can overcome poverty and all the other difficulties our country is facing today."
European Union monitors said on Monday there were serious problems with the polls, but they were probably not sufficient to change the outcome.
Frelimo, which has been in power since independence in 1975, also took 160 out of the 250 parliamentary seats.
Renamo leader Afonso Dhlakama has said his party will not take up their seats in parliament because of fraud.
"We want to alert the Mozambican people that democracy is in danger," said Renamo spokesman Fernando Mazanga.
The BBC's Jose Tembe in Maputo said the results do not come as a surprise as the partial results indicated Frelimo had a big margin.
Armando Guebuza , Frelimo - 63.74%
Afonso Dhlakama, Renamo - 31.74%
Frelimo - 160 seats
Renamo - 90 seats
36% of eligible voters
Following the official election declaration the atmosphere in the Frelimo camp was jubilant and an election victory party is planned, our correspondent says.
But Renamo's reaction was more subdued, with only one representative at the result announcement.
According to Joe Hanlon, an analyst on Mozambican affairs, the opposition has a week to make its objections to the constitutional court.
But he said any challenge was unlikely to change the overall presidential result.
"It would probably change the number of parliamentary seats," he told the BBC's Focus on Africa programme.
"Armando Guebuza has gotten exactly two million votes and Afonso Dhlakama has gotten one million votes," he said.
Mr Guebuza, who is expected to be inaugurated in January, has a reputation for cracking down on corruption, our correspondent says.