More than 2,000 police officers have been deployed in Nairobi during the holy month of Ramadhan beginning on Thursday.
Nairobi regional coordinator Kangethe Thuku said the officers will be in streets, hotels, bus stops and around learning institutions.
Others will man business malls among other public places to heighten vigilance amid threats by terror groups.
Foreigners without valid immigration documents and adults without National identity cards will be arrested.
All PSV passengers must be frisked before boarding PSVs because it is feared terrorists can board and blow up matatus.
Kangethe Thuku and Nairobi police boss Joseph Ole Tito on Wednesday said security officers will be "saturated" by uniformed and non-uniformed- officers to thwart any terror threat.
They spoke at Nyayo house during a press briefing.
Hotels are required to register and keep particulars of all the people seeking accommodation in their premises.
"When terrorists come, they will have to lodge at a hotel somewhere to plan their activities. So the security officers will be visiting all hotels - big and small to scan the visitors' registers and hotels are required to cooperate," Thuku said.
"We have been receiving terror threats and decided to share with the public to be vigilant. Many terrorists are targeting our city. We are here as the government to assure you that your lives and property are protected. We have government buildings which have many people especially Nyayo House. We also have shopping malls, international hotels, bus stops, and this city is vulnerable to terrorists."
He said members of the public can use "Mulika Uhalifu" platform to send alerts through 22068.