Zambian opposition leader Brian Mundubile said on Wednesday that he would challenge this week's presidential election result in court, alleging vote irregularities in the contest that secured President Hakainde Hichilema a second term in office.

"Our campaign has documented serious irregularities, inconsistencies and circumstances surrounding the conduct, counting, transmission and declaration of results", Mundubile said in a statement.

An election strategist for Hichilema declined immediate comment but said he would comment later.

The election commission declared Hichilema the winner with about 60% of valid votes in the early hours of Tuesday morning, compared with 38% for Mundubile.

Tense elections

After a relatively quiet run-up to the August 13 election in the mineral-rich Southern African nation of 22 million people, tensions flared after the polls closed.

Zambian authorities arrested 11 people, including leading opposition figures.

The electoral commission also suspended vote-counting for hours due to reports of violence against polling staff and the theft of ballot papers.