A ban on smoking in Kenya's public places has come into force, to reduce the number of tobacco-related deaths.
Kenya's neighbours have already banned smoking in public places
From Monday, anyone smoking in offices, bus stations, airports and sports venue faces a fine of 50,000 Kenya shillings ($700; £375) or six months in prison.
Bars and restaurants without separate smoking areas are also affected.
Cigarette manufacturers were due to start printing health warnings about the dangers of smoking on cigarette packets but they may appeal in court.
Kenya's 300,000 tobacco farmers, who grow about 20,000 tons a year, fear the ban could seriously hit their incomes.
The BBC's Noel Mwakugu in Nairobi says some of Kenya's five million smokers are in a state of panic, looking for somewhere safe to light up.
Some have described the penalties for smoking in public places as unrealistic.
No arrests have been reported so far.
A spokesman at the police headquarters in Nairobi has told the BBC that police have not yet received specific orders to enforce the new law.
Officials at Nairobi City Council, which is expected to include the new ministry of health directive into its by-laws, did not wish to comment.
The manufacturers say they have stopped producing cigarettes for the local market because they have not had time to print warnings that cover 50% of the packet size, as the new law requires.
British America Tobacco's Kenya spokesman Keli Kiilu said they have sent a protest note to the health ministry asking them to revoke the new directive until consultations are held.
He said the firms may go to court if their plea goes unheard.
Last year, Director of Medical Services (DMS) James Nyikal said tobacco killed some 12,000 Kenyans each year and a public ban would reduce that figure.
Last year the government introduced a 140% tax on cigarettes.
Neighbouring Uganda banned smoking in public places in 2004 but the ban is not strictly enforced, reports the AFP news agency.
Tanzania has also outlawed smoking in public places.