Zambia’s main opposition leader Brian Mundubile and his running mate Makebi Zulu have been accused of treason and detained after being questioned, the Zambia Police Service said on Thursday.

Mundubile and Zulu were questioned “in connection with an alleged offence of treason,” police said. Officers did not provide specifics about the nature of the transgression. The two remain in custody at Lusaka Central Police while investigations continue, according to local outlets.

The detention comes two weeks after Zambia’s presidential election, in which Mundubile finished second to Zambian President Hakainde Hichilema. Official results gave Hichilema about 60% of the vote and Mundubile about 38%. Mundubile rejected the result and said he intended to challenge it in court over alleged irregularities, claims Hichilema has denied.

Tensions rose after the vote when security forces raided Mundubile’s residence in Lusaka. Eleven people, including those associated with the opposition, were detained during the operation, where former transport and communications minister Mutotwe Kafwaya was fatally shot, according to police.

Police Chief Graphel Musamba said the task force encountered “gunfire and resistance from unknown individuals” and returned fire. The government said military-grade weapons, ammunition and other materials intended for use in an armed insurrection were found at the property.

Mundubile rejected the accusations as “total fabrications” and described the raid as an attempt on his life. Following the operation, he and Zulu, citing concerns for their safety, took shelter at the UN offices on Alick Nkhata Road in Lusaka, the local outlet Lusaka Times said. They stayed at the compound until Thursday, when they surrendered to police after receiving assurances from the presidency that they would be afforded due process.

Under Zambia’s Penal Code, treason carries a maximum penalty of life imprisonment. The country abolished the death penalty in 2022.

Hichilema, who first took office in 2021, is due to begin a second five-year term following the latest vote.