Zambian opposition leader Brian Mundubile says he will challenge President Hakainde Hichilema’s re-election in court, alleging serious irregularities in the country’s presidential election.

In a statement on Wednesday, Mundubile said his campaign had documented what he described as significant problems involving the conduct of the election, vote counting, transmission of results and the eventual declaration of the winner.

Hichilema was declared the winner of the August 13 election with about 60 percent of the vote, compared with 38 percent for Mundubile, according to the electoral commission.

Although voting was largely peaceful, the opposition raised concerns over alleged intimidation and restrictions during the campaign. International election observers also reported concerns about violence and intimidation surrounding the election.

Tensions increased after polling stations closed, with authorities arresting 11 people, including senior opposition figures, during a raid in which gunfire was reportedly exchanged while Mundubile was present.

The electoral commission also temporarily suspended the counting of votes following reports of violence against election officials and the theft of ballot papers.

UN High Commissioner for Human Rights Volker Türk expressed concern over the arrests, saying on Wednesday that any detention of opposition figures must comply with international human rights standards and Zambian law.

Hichilema entered the election as the frontrunner after overseeing an economic recovery and progress in restructuring Zambia’s debt. However, his first term also faced criticism over the political environment, with opposition parties and civil society groups accusing his administration of restricting dissent.

His second term is expected to bring renewed pressure for greater accountability, political inclusion and a wider distribution of the benefits of economic growth.

Hichilema is expected to be sworn in within seven days of the electoral commission publishing the official results, which are due by August 24. However, Mundubile’s planned legal challenge could affect the timing of the inauguration.