Kenyan police said Friday that an officer died in the western city of Kisumu from injuries sustained in clashes during opposition protests the day before.

His death late Thursday brings to three the number of people who have lost their lives since the anti-government demonstrations began on Monday last week.

Violence and chaos have ensued, with riot police firing tear gas and water cannon at protesters, while many businesses have been looted, property vandalised and journalists attacked by marauding gangs.

Opposition leader Raila Odinga has called for protests every Monday and Thursday, accusing President William Ruto of stealing last year's election and of failing to control the surging cost of living.

He vowed on Thursday that the action would continue, despite appeals at home and abroad for talks to restore calm.

Police in riot gear faced off Thursday -- the third round of the protests -- against hundreds of demonstrators in several cities including the capital Nairobi and Odinga's lakeside bastion of Kisumu.

"As a result of yesterday's demonstrations, one police officer in Kisumu succumbed to injuries while on duty," Inspector General of Police Japhet Koome said.

According to a police report seen by AFP, the officer was injured when they were "overwhelmed by charging rioters" who were looting a supermarket.

At least 20 police officers were injured across the country on Thursday, Koome added.

Two civilians have also been killed in Kisumu, by suspected police fire, in separate incidents on Monday this week and last.

The international community and religious leaders have appealed for calm, voicing fears of a repeat of the 2007/08 post-election ethnic fighting that claimed the lives of more than 1,100 people.

Meanwhile, at least 25 cases of attacks on journalists "at the hands of state and non-state actors" have been reported during the demonstrations, according to the Media Council of Kenya.

The United States said Friday said it was "deeply concerned" by the reports.

"Protecting press freedom and safety is a cornerstone of democracy," US ambassador to Kenya Meg Whitman said on Twitter.

In a statement Wednesday, eight foreign embassies, including the US and British missions, called on "all leaders and all Kenyans to maintain peace, show restraint, and work toward a swift resolution for the common good of Kenya".

The African Union also appealed Tuesday for calm and political dialogue to end the chaos.