LUSAKA, Zambia – Zambian opposition leader Brian Mundubile and his running mate, Makebi Zulu, have been taken into police custody over alleged offences linked to national security, including treason, authorities said on Thursday.

Mundubile, who finished second to President Hakainde Hichilema in the August 13 presidential election, had been in hiding after police raided his home and other opposition sites following the vote.

The Zambia Police Service said the two opposition leaders had recorded “warned and cautioned” statements in connection with an alleged offence of treason, a serious crime carrying severe penalties on conviction.

Police did not immediately disclose the allegations underpinning the treason investigation.

Police spokesman Godfrey Chilabi told state broadcaster ZNBC that Mundubile and Zulu were being interviewed by a team of law enforcement officers in the presence of their lawyers.

“A statement will be issued once the interview process is concluded,” Chilabi said.

ZNBC reported that the pair had been under the protection of the United Nations in Lusaka before surrendering to police.

Mundubile was summoned for questioning last week over alleged threats to national security. Police have said they wanted to establish possible links between him, Zulu and “various alarming activities … which have the potential to threaten or undermine national security”.

Mundubile has previously dismissed the allegations as fabricated.

His detention comes amid heightened political tensions following an election that he has rejected as fraudulent. Hichilema denies the allegations.

The election was largely peaceful, although the vote-counting process was briefly suspended amid reports of attacks targeting election officials. The Electoral Commission of Zambia declared Hichilema the winner with about 60 percent of the vote, while Mundubile performed better than many observers had expected.

Mundubile briefly claimed victory on election night before Hichilema urged supporters to await the official results.

Police raided Mundubile’s home and other opposition sites the day after voting, arresting 11 people. Former cabinet minister Mutotwe Kafwaya was shot dead during an exchange of gunfire in the operation, while Mundubile went into hiding.

Mundubile, leader of the National Reconciliation Party for Unity and Prosperity, subsequently maintained that the election had been rigged and said the security allegations against him were politically motivated.

His detention also follows a controversial shutdown of Zambia’s judiciary earlier last week.

On August 17, the final day for filing presidential election petitions, authorities closed the High Court and other courts across the country, citing security concerns. The move forced the postponement of court proceedings and drew condemnation from lawyers, opposition parties and rights groups.

The developments have raised fresh concerns over Zambia’s democratic record. The country has traditionally been regarded as one of Africa’s more stable democracies, but tensions following the election have tested that reputation.

Hichilema is due to be sworn in for a second term on September 1.