Patriotic Front leader Michael Sata (above) lost the 2008 elections to Rupiah Banda by 2 per cent [EPA]

Opposition leader Michael Sata has been declared the winner of Zambia's presidential election, ousting incumbent Rupiah Banda as the leader of Africa's biggest copper producer in polls marred by public violence.

Chief Justice Ernest Sakala declared Sata the winner early on Friday, after he received 1,150,045 votes compared to Banda's 961,796 with 95.3 per cent of constituencies counted. Sata received 43 per cent of the vote also contested by many minor parties.

Rupiah Banda, the leader of the Movement for Multi-party Democracy (MMD) party that has run Zambia since one-party rule ended in 1991, conceded electoral defeat, saying "the people of Zambia have spoken and we must all listen."

"Now is not the time for violence and retribution. Now is the time to unite and build tomorrow's Zambia together," he said in a news conference.

"My generation, the generation of the independence struggle, must now give way to new ideas, ideas for the 21st century."

Sata supporters spilled into the streets in the capital Lusaka after the announcement, singing and chanting in celebration.

Youths fought running battles with riot police on Thursday in the towns of Ndola and Kitwe, 250km north of Lusaka, setting fire to vehicles and markets in the normally peaceful southern African country's mining heartland.

Hackers who hit the Election Commission's website overnight, posting false results showing Sata on course for a landslide, added to the confusion and tension of what was already a tight race between two old rivals.

Chinese companies have become major players in Zambia's economy, with total investments by the end of 2010 topping $2 billion, according to data from the Chinese embassy. 

But Sata accused Chinese mining firms in the earlier stages of the campaign of creating slave labour conditions with scant regard for safety or the local culture.

Analysts said younger voters also helped propel him to victory with youth using the ballot box to bring about change in a continent that has seen the long-standing rulers of Egypt and Tunisia toppled by mass street protests.

Sata lost to Banda by just 35,000 votes, or 2 percent of the electorate, in a 2008 presidential run-off triggered by the death in office of Levy Mwanawasa.