Anti-terrorism police are interrogating four suspects over the Friday afternoon twin blasts at Gikomba market that left at least 12 people dead.
Nairobi County Commander Benson Kibue said three of the suspects were students from Comoros Island while one was a Kenyan identified as Joseph Wanjiru.
The suspects were arrested shortly after the blast that claimed 12 lives and injured over 80 people.
Inspector-General of Police David Kimaiyo has also said security agents have enhanced security across the country with special focus on diplomatic missions following the recent terror attacks.
Elsewhere, three of the four suspects behind the May 4 blast along Thika Superhighway have been arrested after two weeks’ hunt in a well-coordinated covert operation.
One of the suspects was arrested at the Liboi border as he was crossing over to Somalia.
According to intelligence reports, the attackers crossed over to Somalia last year where they trained for about eight months.
They came back into the country on May 2, just two days before they planted the Improvised Explosive Devices (IEDs) in the Githurai and Kasarani-bound vehicles.
However, detectives are still looking for the fourth suspect who is still at large.
The deputy commandant of the Diplomatic Police Unit (DPU), Mr Ambrose Mwawaka, on Saturday told the Sunday Nation that security had been enhanced especially in Gigiri.
The US has also provided additional security personnel. Armed US marines have also joined the General Service Unit (GSU) and the DPU officers in patrolling the area.
On Friday, the United States Ambassador in Kenya, Mr Robert Godec, asked for additional Kenyan and American security personnel.
Police have also warned of the possibility of secondary attacks and warned members of the public against milling around such scenes.
“I want to urge members of the public who may have any information in respect to this incident to come forward and share the same with the police. They should also desist from crowding or milling around scenes of crime for their own safety,” said Mr Kimaiyo.
The US has been joined by other countries like Britain, France and Australia who have also warned their citizens of possible terror attacks in Nairobi and Mombasa. However, there are no specific details regarding the potential attacks.
Even the US Embassy in Nairobi admitted to its citizens that they did not have the fine details of the targeted places.
“While there is no specific information regarding the stage of any attack, preparations, targets, or timing towards US citizens, we would like to remind US citizens that targets for these attacks could include hotels, nightclubs, shopping malls, diplomatic missions, transportation hubs, religious institutions, government offices, or public transportation,” read the notice.
Mr Godec had regretted that the security situation in Kenya, especially in Nairobi and Mombasa, continued to worsen.