Officials in Zambia are counting votes from Tuesday's general election, including the closely-watched presidential contest between incumbent Rupiah Banda and opposition leader Michael Sata.

Initial tallies Wednesday showed Mr. Sata taking an early lead, but most of Zambia's 150 constituencies have yet to report their results.

Pre-election surveys suggested a close race between Mr. Banda, who leads the ruling Movement for Multiparty Democracy , and Mr. Sata of the opposition Patriotic Front.

Scattered incidents of violence were reported Tuesday in the capital, Lusaka, but European Union election observers say the vote was conducted in a “correct” manner. EU chief election observer Maria Muniz described the election as fair and transparent.

Ahead of the poll, Mr. Sata accused the electoral commission of planning to rig the outcome using pre-marked ballots. The electoral commission denied that allegation.

President Banda campaigned on a record of several years of strong economic growth in copper-rich Zambia, which has benefited from a boom in global commodity prices. Mr. Sata's Patriotic Front accused Mr. Banda of tolerating corruption and not doing enough to ensure that more Zambians share in the wealth of the country's copper reserves.

Mr. Banda defeated Mr. Sata by two percentage points in a 2008 special election to complete the term of late President Levy Mwanawasa, who had died of a stroke.

Mr. Banda had served as Mr. Mwanawasa's deputy. Mr. Sata disputed the results, and his supporters rioted for days afterward.

More than five-million Zambians were registered to vote in Tuesday's presidential, parliamentary and local elections.