The Electoral Commission of Zambia (ECZ) announced the final
results after his challenger, Michael Sata, conceded defeat.
Mr Sata has accused President Mwanawasa of stealing the election but he has urged his supporters to remain calm.
Unrest continues
There has been a second night of violence and clashes between police and supporters of Mr Sata’s Patriotic Front.
The unrest forced the commission to delay announcement while police were deployed in anticipation of wider violence.
Banks and businesses were forced to shut their doors in response.
In the opposition stronghold of Lusaka, police fired teargas to disperse protesters who had gathered in the Garden township.
"We are not going to do anything to destroy Zambia, and I ask
the people to keep calm even if they are angry," Mr Sata said.
He warned earlier of dire consequences when he first raised charges of vote rigging.
"Levy has stolen victory, but this is just a temporary setback
because we are going to fight on."
In contrast, Mr Sata's stronghold in the Copperbelt region, the hub of Zambia's mainstay copper production, was calm.
Official results
The Electoral Commission’s chairwoman Ireen Mambilima has said Mr Mwanawasa took 1,177,846 of the votes counted or 43 per cent.
Mr Sata scored 804,748 votes or 29 per cent. Wealthy businessman
Hakainde Hichilema came third on 693,772 votes, or 25 per cent.
Nearly four million people had registered to vote and some 2.7 million turned out for the presidential and parliamentary polls on Thursday.
Chief Justice Ernest Sakala immediately declared Mwanawasa the
Winner.
The president is expected to be inaugurated tomorrow for a second five-year term which will be his last under constitutional rules.
Poor result for opposition
Sata had looked set to sweep Mwanawasa from power on the back of
strong support from Zambia's poor.
Many are angry that economic reforms have not brought a better life for them.
More than two thirds of Zambians live on less than $US1 ($A1.35) a day.
Mr Sata said his Patriotic Front would wield significant political
clout as it was set to control key municipalities in Lusaka and the
Copperbelt.
"We are going to run the councils as corporate bodies and
totally ignore the minister of local government," he said in a
threat of looming friction with the central government.
The Electoral Commission of Zambia has promised results of voting for the national parliament and municipal councils for Tuesday.
The Southern African country is accustomed to accusations of
vote fraud -- most recently in the 2001 elections that brought
Mwanawasa to power.
But Zambia has largely escaped the political violence that has dogged many other African countries.
Sata is a 69-year-old populist who has praised the controversial
land policies of Zimbabwe's Robert Mugabe, had vowed to get tough
with Chinese investors.
Mr Mwanawasa, 58, campaigned on his economic record, which includes winning billions of dollars in debt relief and boosting economic growth to above five per cent.