LUSAKA, Zambia — Chinese shopkeepers barricaded their properties against gangs of looters in Zambia’s capital, Lusaka, yesterday as a presidential election sparked a backlash against Beijing’s growing influence in Africa.

An opposition candidate, Michael Sata, won 29% of the vote after accusing China of “exploitation” and turning Zambia into a “dumping ground.”

Although President Mwanawasa was re-elected with 43% of the vote, Mr. Sata won in areas most affected by Chinese investment. In Lusaka, he polled almost three times as many votes as the president. China has become one of the key foreign powers in Africa as it searches for raw materials to fuel its economy.

Chinese immigrants have opened many shops in Lusaka, where the Chinese community has grown tenfold to about 30,000 in the past decade.

But the presence of Chinese immigrants has sparked great resentment. Chinese businessmen are accused of underpaying their workers, ignoring safety rules, and driving local companies out of business with cheap and shoddy goods.

Last year, 46 miners died in an accident at Chambishi, a copper mine owed by Chinese investors. Three months ago, its workforce rioted over low wages and poor conditions. The leader of the Patriotic Front, Mr. Sata, claimed yesterday that Mr. Mwanawasa had “stolen victory.” He mobilized these grievances behind his presidential campaign.

“We want to work with the Chinese, but they must change,” he said.

“Their labor relations are very bad. They are not adding any value to what they claim is investment. Instead of creating jobs for the local workforce, they bring in Chinese workers to cut wood and carry water.

“We don’t want Zambia to be a dumping ground for their human beings.”

When it became clear that Mr. Sata had lost the election, riots broke out in his Lusaka strongholds. Mr. Sata said the government had “robbed” him of victory by “stealing votes” from under the noses of “timid and toothless” election observers from the European Union.

Resentment over what his supporters believe was a “rigged” election caused the unrest. But looters soon began targeting Chinese-owned shops.

In Kamwala market, the Chinese owner of a clothes store locked his heavy metal door as looters ran down the street, carrying their booty.