A Kenyan government minister has alleged that the country's national intelligence agency was behind the abduction of his son last year, as criticism against the rising cases of abductions continues.

Public Service Cabinet Secretary Justin Muturi said that it took a call by President William Ruto to have his son released by the National Intelligence Service (NIS).

Muturi is the first member of the cabinet to publicly criticise the government's handling of the spate of abductions in Kenya.

In a statement to the police crime investigations unit on Tuesday, Muturi gave a detailed account of how his son, Leslie, was abducted on 22 June last year.

Mr Ruto and the intelligence agency have not commented on his allegations.

At least 80 people, including the minister's son, have been abducted in the last six months, according to a state-funded rights group.

The wave of abductions started after protests against tax hikes last June, and have continued since then.

Some of those abducted have been released following public pressure.

Earlier this week, the minister told journalists that he had not received answers about the abduction of his son, despite reaching out to top security officials.

Muturi said the Directorate of Criminal Investigations (DCI) subsequently urged him to record a statement with them, telling him the matter was still under investigation.

In his statement to the DCI, Muturi recalled calling the inspector-general of police, the interior minister, the DCI head, the head of the intelligence agency and other top officials as he desperately looked for his son – but, he added, all were unable to help.

He said that he also messaged Ruto but later decided to visit his official residence to raise the matter directly with him.

"I then narrated the ordeal [to the president] including my interactions with various senior government officials who had been unable to help. I expressed my belief that NIS was holding my son," Muturi said in the statement.

He said that the president made a joke about the issue and then made a call to the head of the intelligence agency, who promised to release his son in an hour.

"I heard the president ask [NIS director] Noordin Haji if he was holding my son. [He] confirmed that indeed he was holding my son and the president instructed him to release Leslie immediately," Muturi added.

Muturi has faced calls from some government-allied politicians to resign for publicly criticising the government in which he serves.

Foreign nationals have also been abducted, including prominent Tanzanian activist Maria Sarungi Tsehai, who on Monday narrated how she was kidnapped by armed men and released several hours later.

Last year, Ugandan opposition leader Kizza Besigye was kidnapped in Kenya's capital, Nairobi, allegedly by Ugandan security officials, and taken across the border for trial by a court martial.

Muturi's public mentioning of Ruto's name in connection with abductions is a defiant challenge to the president and is seen as being against the principle of collective responsibility in government.

It has also fuelled speculation of a fallout in government, with other ministers and officials often denying that the abductions are being carried out by the state.

Amid public uproar, the president said towards the end of last year that "we are going to stop the abductions", while advising parents to instil good values in their children.

He has also warned young people not to use social media to disrespect leaders, amid continued widespread online criticism of the government.