Police in the Kenyan capital Nairobi have fought running battles with university students protesting about an increase in fees.
A BBC reporter in the city said teargas was fired during a standoff that lasted for several hours.
Police entered the campus of the University of Nairobi and several student union representatives were arrested.
Meanwhile rioting students blocked a major highway in western Kenya.
They caused hold-ups on the road linking the city of Kisumu, on Lake Victoria, to neighbouring Uganda, the BBC's Wanyama wa Chebusiri reports.
But the University of Nairobi was the most severely affected by the nationwide strike against a proposed fee hike, our correspondent says.
Armed riot police fired tear gas at students who responded by throwing stones.
A number of people are believed to have been injured.
Businesses in downtown Nairobi were closed on Tuesday and a section of the city remained a total no-go zone, our correspondent adds.
One protesting student, Titus Khaemba, told the Associated Press he thought the Kenyan government should be focusing on security threats and the economy rather than raising fees.
"Right now there is no employment along the coast and the government is not looking into that," he said.
"They are looking on how to get the money for the next election," he added.
Similar scenes were reported in towns including Kakamega and Nakuru, according to Kenyan newspaper The Standard.