Zambian police have summoned opposition leader Brian Mundubile for questioning over alleged national security threats in the latest escalation of a post-election dispute that analysts say may tarnish the country's democratic reputation.

The August 13 poll was widely expected to result in a smooth re-election for President Hakainde Hichilema, who took power in 2021 in the mineral-rich Southern African nation.

Hichilema won 60% of votes, according to the electoral commission. But the opposition put in an unexpectedly strong showing, and in the days that followed opposition figures were arrested amid allegations of vote-rigging.

Two reports by independent observers found indications that Hichilema's vote count was inflated, but that he would have won anyway. Hichilema denies any fraud.

Mundubile, who plans to challenge the results in court, has gone into hiding.

OPPOSITION FACES DEADLINE TO FILE COURT CHALLENGE

In a statement late on Thursday, police said they wanted to interview Mundubile and his running mate, Makebi Zulu, who they said had sought refuge "under international law with a known international organisation".

The purpose would be to establish links between the two and "various alarming activities... which have the potential to threaten or undermine national security," it said.

Security forces raided a property where Mundubile was present last Friday and arrested 11 people, some of whom were his associates, accusing them of possessing materials for an armed insurrection. Ex-minister Mutotwe Kafwaya was shot dead in an exchange of gunfire during the operation.

The government has not brought charges or publicly produced evidence to support the allegations, drawing condemnation from international organisations.

Mundubile could not be reached for comment, but has previously dismissed the allegations as fabricated.

Nicole Beardsworth, a politics lecturer at the University of the Witwatersrand in Johannesburg, said the post-election fallout was surprising, given that Hichilema had been expected to win re-election.

"This is completely out of the bounds of the ordinary for Zambia," she said.

The opposition has until early Tuesday one week after the results were announced - to file an election challenge in court. But the arrests of senior party members and the police summons may make that difficult, said Beardsworth.