Kenyan police fired dozens of teargas canisters into a crowd of thousands of opposition protesters on Friday as they attempted to march into the main business district of the capital to protest over tax hikes.

Opposition leader Raila Odinga called the protests to oppose tax increases that have been imposed at a time when many are already struggling with high prices of basic commodities such as maize flour.

Kenya's High Court ordered that the tax hikes be suspended but the government has raised petrol prices anyway, leading to a further court challenge.

Odinga addressed a crowd of about 2 000 supporters at an open air ground just outside of the main business district at lunchtime. He accused the government of failing to tackle the high cost of living, poaching opposition lawmakers and unilaterally reconstituting the election commission.

He said they would then march to another park in the main business district. But police then started firing teargas to stop the crowd, some of whom threw rocks at the police before turning back.

Local media outlets had reported that the protesters were not allowed to enter the main business district, quoting the head of Nairobi police, Adamson Bungei.

Television news channels also showed footage of police firing teargas canisters to disperse protesters in the port city of Mombasa and other towns including Kisii in the west.

President William Ruto's government says the tax hikes, expected to raise an extra 200-billion shillings ($1.42-billion) a year, are needed to help deal with the country's growing debt repayments, and fund job-creation initiatives.

Police have allowed the opposition's main rally to go ahead, but warned against the destruction of properties and businesses.

National police spokesperson Resila Onyango did not respond immediately when Reuters sought further comment.

Odinga gave his initial address at the historic Kamukunji ground in the capital - the scene of intense clashes between the police and agitators for multi-party democracy 33 years ago to the day.

The High Court suspended the implementation of the finance law last week but the government raised the retail prices of petrol anyway, forcing the opposition senator who lodged the case to seek the jailing of the head of the energy sector regulator for contempt.

The court will rule on the contempt application on Monday and give further directions on the main suit on the same day.