Michael Sata has been sworn in as Zambia's president after an upset election victory that has ushered in a handover of power in Africa's biggest copper producer.
Sata, the 74-year-old Zambian opposition leader, swept to victory on Friday on the back of voters hoping profits from the country's vast mineral deposits would finally make their way to the people.
Foreign mining firms were reassured by Sata that their investments would be safe, but he warned them to improve conditions for their Zambian workforce.
"Foreign investment is important to Zambia and we will continue to work with foreign investors who are welcome in the country ... but they need to adhere to the labour laws," Sata said after being sworn in following his defeat of former leader Rupiah Banda.
Zambians celebrated from the pre-dawn hours of Friday after Sata was declared the winner and painted the capital in the green and white int the colours of his Patriotic Front Party.
Al Jazeera's Gladys Njoroge, reporting from Lusaka, said people poured into the streets to applaud the victory win although the process was marred by violence due to delayed results and allegations of vote rigging.
Sata told the gathered crowd: "We should not allow violence to separate us. The gap between the rich and the poor is growing wider and we need to address that. I stand by the promise to change Zambia within 90 days."
In a continent where leaders are often reluctant to give up power, Banda tearfully conceded defeat, saying the people had spoken. His Movement for Multi-party Democracy (MMD) party has run Zambia since one-party rule ended in 1991.
"Now is not the time for violence and retribution. Now is the time to unite and build tomorrow's Zambia together," he told a news conference.
In his concession speech, Banda may have been delivering a message to Zimbabwe, Malawi, Angola and the Democratic Republic of the Congo, where entrenched leaders have suppressed democracy or used deadly force to crush protests.
"My generation, the generation of the independence struggle, must now give way to new ideas; ideas for the 21st century," Banda said.
"Did we become gray and lacking in ideas? Did we lose momentum? Our duty now is to go away and reflect on any mistakes we may have made and learn from them. If we do not, we do not deserve to contest power again," the 74-year-old Banda said.
Election monitors from the European Union and regional groups declared the vote free and fair although protests broke out over the slow release of results.
Analysts said Sata would review contracts with foreign companies struck by Banda's administration, and could overhaul the country's mining, trade and banking regulations.
"Sata's upset victory will likely usher in a new era for a resource-nationalist mining sector policy," said Sebastian Spio-Garbrah, an analyst at Africa consultancy DaMina Advisors.
Ernest Sakala, Zambia's chief justice, declared Sata the winner after he received 1,150,045 votes compared with Banda's 961,796 with 95.3 per cent of constituencies counted. Sata received 43 per cent of the vote, which was also contested by many minor parties.
Sata has enjoyed a long and varied career that included stints in motor vehicle assembly plants in Britain and as a porter with British Rail before becoming a political activist under first president, Kenneth Kaunda.
"At long last, the will of the people has been respected. The people wanted change," said street vendor Peter Musonda.
Sata secured support among the youth on promises to create jobs and his criticism that Banda's government failed to let ordinary Zambians share in the proceeds from the country's copper mines.
China welcomed the outcome of the vote and said it would continue fostering cooperation.
Its companies have become major players in Zambia's $13 billion economy, with total investments by the end of 2010 topping $2 billion, according to data from the Chinese embassy.
But Sata has accused Chinese mining firms of creating slave labour conditions with scant regard for safety or the local culture.
Zambia's currency, the kwacha, fell 2.9 per cent to a 14-month-low of 5,150 against the dollar after Sata's victory and traders said it would remain vulnerable until he gave clearer indications on his future policies.
South Africa congratulated Sata on his election victory, saying the peaceful change of power bodes well for democracy on the continent.
"This bodes well for the consolidation of democratic culture on the continent and in Zambia particularly," South Africa's foreign ministry said in a statement.
"The South African government and its citizens reiterate its commitment to continue working with the government and the people of Zambia for the mutual benefit of the two countries," it said.
Zambia is South Africa's fourth-largest trading partner in Africa, with a total trading volume of $2.1 billion, according to the Zambia Chamber of Commerce.