Matatus, the minibus taxis used by so many Kenyans to navigate the capital Nairobi, often covered in graffiti and modified with extra-loud horns, are facing a crackdown from regulators.

Offensive graffiti, noisy modified exhausts, horns and sound systems are all being targeted by the country's transport and safety authority (NTSA).

Vehicles flouting the rules will be pulled off the road, the NTSA says.

President Uhuru Kenyatta has previously said he supports artwork on matatus.

The extra decoration or "pimping" of matatus is viewed by many as an important aspect of cultural life in the capital.

Matatu owners choose everything from politicians to sports teams to film stars and musicians as themes for their vehicles

However, the NTSA is unhappy about the decoration on some matatus, which it deems "excessive and vulgar", making it harder to identify which bus operator the vehicle belongs to.

Owners, operators and drivers of matatus caught flouting the regulations face arrest and fines, with possible jail terms if they fail to pay up.

Extra traffic police are out on the roads to enforce the plan, the BBC's Odhiabmbo Joseph reports from Nairobi.

There are fears that the crackdown by traffic police, who are notoriously corrupt, will simply be used as an excuse to solicit bribes, our correspondent adds.

Previous attempts to clean up the matatus have not been effective.

Speaking to the BBC, Patrick Oma, who works at one of the city's matatu parks, conceded that the move to reduce noise pollution from modified exhausts was "not a bad idea".

However, graffiti, he says, "doesn't cause accidents" and has "created jobs for young people".