Prominent Kenyan activist Boniface Mwangi is due in court on accusations of "facilitation of terrorist acts" during last month's deadly anti-government protests in which at least 19 people died.

On Sunday, investigators said they had seized phones, a laptop, and notebooks from Mr Mwangi's Lukenya home on the outskirts of the capital, Nairobi, and hard drives, computers, tear gas canisters and a blank firearm round from his office in the city.

His arrest has sparked a wave of condemnation, with human rights groups denouncing it was aimed at suppressing opposition voices.

The activist has denied the accusations, saying in a post on X: "I am not a terrorist."

According to Kenya's Directorate of Criminal Investigations, Mr Mwangi stands accused of "offences related to facilitation of terrorist acts and unlawful possession of ammunition".

The alleged offences are linked to the 25 June protests when, according to the state-funded Kenya National Commission on Human Rights (KNCHR), 19 people died when demonstrators clashed with police. Hundreds were also injured and property and businesses were damaged.

In the aftermath, Interior Minister Kipchumba Murkomen described the demonstrations as "terrorism disguised as dissent" and an "unconstitutional attempt" to change the government.

At least 38 more people were killed in subsequent protests earlier this month, the KNHCR has said.

Since June last year, more than 100 people have been killed in successive waves of anti-government protests, with police accused of using excessive force to quell unrest.

On Sunday, a coalition of 37 rights organisations condemned Mr Mwangi's arrest on "unjustified terrorism allegations", describing it as the "latest escalation in a systematic crackdown that has seen hundreds of young Kenyans detained on fabricated terrorism charges".

"What began as targeted persecution of young protesters demanding accountability has metastasized into a full-scale assault on Kenya's democracy," they said in a joint statement.

James Orengo, a veteran politician and governor of Siaya county, said it was "ridiculous to charge Boniface Mwangi and our children who have demonstrated a high level of political consciousness with terrorism".

Mr Mwangi has been detained multiple times in the past, and has been at the centre of many protests.

In May, he and a Ugandan activist Agather Atuhaire were detained in Tanzania, where they had travelled to attend the trial of Tanzanian opposition leader Tundu Lissu, who is accused of treason.

Following their release several days later, both said they had been abducted, tortured and sexually assaulted. They have since filed a case at the regional East African Court of Justice over the matter.