(AFP) - Kenyan officers on Wednesday fired tear gas on protesters who defied a police ban to join a demonstration against tax hikes called by opposition leader Raila Odinga.

Shops were shut and security was tight in the capital Nairobi, where police deployed tear gas against stone-throwing demonstrators in the slum of Mathare. Tear gas was also used to disperse crowds in the port city of Mombasa.

The clashes followed rallies in several cities last week that turned deadly. Six people were killed according to the interior ministry, and rights campaigners accused police of being heavy-handed.

On the eve of Wednesday's protests, the country's police chief warned opposition supporters from holding "illegal demonstrations", saying that organisers had not provided the authorities with any "notifications" about their planned rallies this week.

"In this regard, no such demonstrations/gatherings/protests will be allowed tomorrow... All lawful means will be used to disperse such demonstrations," Inspector General of Police Japhet Koome said in a statement.

Police in Nairobi on Friday fired tear gas, targeting Odinga's convoy, AFP reporters reported.

They took similar steps against demonstrations in the cities of Mombasa and Kisumu.

On Saturday campaigners said police used tear gas on civil society representatives demanding the release of dozens of people arrested during the protests.

The Kenya National Commission on Human Rights has called for "a thorough investigation into all reported incidents of police brutality", adding to the chorus of condemnation from rights groups including Amnesty International against "arbitrary arrests".

Odinga's Azimio alliance has vowed to stage protests every week against the policies of President William Ruto's government.

"Our activities are protected by the Constitution which guarantees right to protest, picket, assemble and present petitions," Odinga's spokesman Dennis Onyango told AFP.

- 'Life getting worse' -

Odinga, who lost the August 2022 election to Ruto, claims that the poll was "stolen" and has held a string of anti-government rallies this year.

But as soaring food prices pile pressure on households, many Kenyans said they could not afford the disruption caused by the protests and had little hope of seeing improvements to their economic situation.

"I used to look forward to the protests, I felt it was the only way our voices were being heard but nothing is changing," housekeeper Ruth Nyakundi told AFP on the eve of the demonstrations.

"Life is just getting worse," the 41-year-old said.

Shopkeeper Lameck Mwangi, 34, told AFP he had decided to close his electronics store in downtown Nairobi for the day.

"We all know where it ends when we see deserted streets like this and police patrolling town. Let me just go home and watch what will unfold on TV," he said.

Ruto last month signed into law a finance bill expected to generate more than $2.1 billion for the government's depleted coffers.

The Finance Act provides for new taxes or increases on basic goods such as fuel and food and mobile money transfers, as well as a levy on all taxpayers to fund a housing scheme.

The government says the taxes will help create jobs and reduce public borrowing.

The Nairobi high court had suspended implementation of the legislation after a senator filed a case challenging its constitutional legality.

But Kenya's energy regulator announced a hike in pump prices after the doubling of VAT to 16 percent as stipulated in the law.

© Agence France-Presse