A Nepal court extended the detention of former prime minister KP Sharma Oli and his ex-home minister for a further five days on Sunday as investigators examine their alleged roles in a deadly crackdown on protests last year.

Police arrested Oli, 74, and former home minister Ramesh Lekhak on March 28, a day after Prime Minister Balendra Shah was sworn in following the first elections since the September uprising that toppled Oli's government.

Authorities are investigating their alleged involvement in the crackdown on demonstrations that killed at least 76 people. 

Neither man has been formally charged and both deny responsibility for the violence.

"The court has granted five days' extension," Kathmandu District Court information officer Deepak Kumar Shrestha said.It was the third extension of their detention and the court said more investigation was needed after statements were given by Oli and Lekhak. 

It was the third extension of their detention and the court said more investigation was needed after statements were given by Oli and Lekhak. 

"It seems reasonable to keep the defendants in custody for the purpose of the aforementioned investigation," it said. 

Oli has been in hospital since soon after his arrest for what police described as a procedural medical check‑up, adding that he suffers from heart and kidney problems.

Nepal's Supreme Court is also reviewing a petition filed by Oli's wife claiming his detention was unlawful.

The arrests of Oli and Lekhak came after an inquiry commission recommended prosecuting the four-time ex-prime minister and other officials for failing to stop security forces from opening fire on demonstrators.

The commission's report said statements given by the two men suggesting they did not know about the violence were part of a bid to shift responsibility and amounted to "criminal negligence".

Oli's CPN-UML party has described the arrests as "a vengeful act" and called for protests.

The unrest began in early over a brief social media ban but tapped into longstanding anger over economic hardship.

It spread nationwide the following day as parliament and government offices were set ablaze, resulting in the collapse of Oli's government.

Shah, a 35‑year‑old rapper-turned-politician, won a sweeping election victory on a platform of youth-driven political change and defeated Oli in his own constituency.