Kenyan police fired volleys of tear gas on Thursday in the heart of the capital Nairobi as small groups of protesters gathered on what was billed as a fresh day of action against President William Ruto.

Reporters saw riot police patrolling the streets of the central business district, as roadblocks were set up on major arteries with many shops shut.

The East African nation, one of the most stable in the region, has been rocked by weeks of sometimes deadly protests against Ruto's two-year-old administration, mostly led by young Gen-Z Kenyans.

While Ruto was overseeing the swearing-in of a revamped cabinet, just a few kilometres away, police were seen lobbing tear gas in the central business district and detained several people.

Television footage from the Indian Ocean city of Mombasa also showed traffic flowing normally with no signs of trouble, as the western lakeside city of Kisumu was also reported to be calm.

Kenya's acting police chief Gilbert Masengeli had warned that "criminals" intended to infiltrate the demonstrations and advised people to stay away from protected zones such as the main international airport and Ruto's official residence and take precautions in crowded areas.

What started out as peaceful youth-led rallies against controversial proposed tax hikes ballooned into wider action against Ruto and what many see as profligate government spending and corruption.

Reports have it that at least 60 people have been killed since the protests began in mid-June, with police accused of using excessive force, sometimes firing live bullets, while dozens of people have gone missing, according to rights groups.