In the capital Nairobi, protesters who had donned white t-shirts with red spots to symbolize bloodshed, gathered at Freedom Corner in Uhuru Park. They waved placards condemning extrajudicial killings and called for an end to police impunity.

According to Kenya's Daily Nation, three police officers suspected in the killing of human rights lawyer Willie Kimani, his client and a taxi driver will remain in custody for the next 14 days pending investigations. The case is set for hearing on July 18.

The slain bodies of Kimani and the two others were discovered on July 1, in a river in Machakos County, after he reportedly visited a police station in Machakos. Kimani was an advocate at the High Court and a member of the Law Society of Kenya (LSK).

LSK Chairman Isaac Okero told DW that the lawyers intend to protest the entire week to send a clear message on what he described as a very serious problem. "It is absolutely intolerable and unacceptable that this [extra judicial killing] situation continues to pertain," Okero said.

Okero warned that, if unaddressed, the deteriorating security situation could become a threat to the rule of law and a complete erosion of constitutional rights. "The latest incident is perhaps the most significant illustration of what we can say is the systematic failure of security structure," Okero said.

"The latest incident is an indication that there is no Kenyan who is not exposed to this potential threat of elimination," Okero added.

Kenyan political commentator Patrick Gathara told DW that he doesn't think the protests will achieve much. "We have had complaints about extrajudicial executions by police and even extrajudicial harassment by police for a very long time," Gathara said. "This is all part and parcel of a wider effort to put more pressure on government to enact the reforms within the police force," Gathara added.

Amnesty calls for investigation

In a press release on Monday, rights group Amnesty International called for a speedy and thorough investigation into the murders which have shocked the nation and exposed the state of human rights in the east African nation.

"These extrajudicial killings are a chilling reminder that the hard-won right to seek justice for human rights violations is under renewed attack," said Muthoni Wanyeki, Amnesty International's Regional Director for East Africa, the Horn and the Great Lakes.

Amnesty also called on the US, UK and Sweden - Kenya's international partners who have been supporting the Kenyan security forces - to be more vigilant of how their aid was being spent in relation to human rights violations. The rights group warned that without insisting on accountability for human rights violations, donor countries would also be complicit in those violations.

George Kegoro, Executive Director of the Kenya Human Rights Commission, said the case should be addressed by all levels of society including the top leadership. "The killing of these three young Kenyans in cold blood should concern President Uhuru Kenyatta," Kegoro said. He called on the head of state to immediately institute a full judicial commission of inquiry into the appropriation and misuse of police resources and personnel for criminal ends "including, as in this case, extrajudicial killings."

There have been increasing calls by lawyers, human rights and civic activists for the country's police chief, Joseph Ole Nkaissery to resign.

Unresolved murders

Kenya has a long history of unresolved murders which date back to few years after independence.

Pio Gama Pinto: Kenyan politician of Indian descent, journalist and freedom fighter. Killed on February 25, 1965.

Tom Mboya: Kenyan politician under late president Jomo Kenyatta's government. Killed on July 5, 1969.

JM Kariuki: Nyandarua lawmaker and assistant minister in Jomo Kenyatta's government. Went missing on March 2, 1975, only for his burnt body to be discovered by Maasai herders at the foothills of Ngong forest inside an ant's nest.

Robert Ouko: Foreign Affairs Minister under former president Daniel Arap Moi. Went missing on February 10, 1990, from his rural home in Kisumu. His body was found a day later, just a few kilometers from his farm at the foothill of Got Alila. It had been burnt beyond recognition.

Julie Ward: British tourist murdered in Kenya's sprawling Maasai Mara game reserve. Her mutilated body was found on September 13, 1998.

Bishop Alexander Muge: Fierce critic of president Moi's then single ruling party KANU. Killed in a mysterious car accident after being warned by a cabinet minister not to step foot in Busia or he "would not leave alive."

Mesheck Yebei: Was reportedly a witness for the Kenyan case at the ICC, but it is not known whether he was to testify for the prosecution or defense. Went missing from his Eldoret home in December 2014. His badly mutilated body was found in Tsavo National Park on March 2015.

Sheikh Abubakar Shariff aka Makaburi: The fiery jihadist Muslim preacher was shot dead by unknown gunmen on April 1, 2014 in Mombasa. He had earlier predicted his own death after he was linked to Somali Islamist group al-Shabab.

Aboud Rogo: Another outspoken Muslim preacher. Rogo was also felled by a hail of bullets by unknown gunmen. He too had been accused of recruiting for al-Shabab.

Caleb Juma: Prominent Nairobi businessman, who had previously warned that his life was in danger, shot dead in cold blood on May 5.

James Shimanyula contributed to this article.