A former Zambian minister was killed in last week's raid by security forces on a house linked to opposition leader Brian Mundubile a day after the presidential election, the authorities have said.

A police spokesman said Mutotwe Kafwaya was fatally wounded by law enforcement officers during what officials have described as an exchange of fire in a security operation in the capital, Lusaka, on Friday.

Eleven people were arrested in the raid, with the authorities accusing Mundubile's party, the NRPUP, of being "involved in insurgency" and "militia activity" and storing "high-grade" weapons.

Mundubile, who has since gone into hiding, rejected the allegations as "total fabrications".

According to official results, incumbent President Hakainde Hichilema won a second five-year term with a 60% share of the vote. Mundubile, who trailed behind with 38%, plans to challenge the outcome in court after alleging the tallying process had been tampered with.

Speaking about Kafwaya on Tuesday, the opposition leader said he had had no information of his whereabouts after he had been shot during the raid, which he said took place at his house.

The police confirmed Kafwaya's death late on Wednesday amid growing demands for information about him.