At least 12 people were killed and hundreds more were left injured in Kenya on Wednesday following nationwide anti-government protests.

According to the Kenya National Commission on Human Rights, all the deaths reported were from gunshot wounds, with more than 400 casualties recorded across the country, which included demonstrators, police officers and journalists.

The protests were organized to mark one year since Kenyan youth stormed parliament at the peak of anti-government demonstrations. Wednesday's protest saw thousands of young people take to the streets across Kenya to commemorate last year's youth-led demonstrations against tax rises. It is alleged by rights groups that at least 60 people were killed by security forces in last year's disturbances.

"There was widespread police deployment across various counties," Raymond Nyeris, the vice-chairperson of the Kenya National Commission on Human Rights, said in a statement late Wednesday.

"There are allegations of excessive use of force, including the use of rubber bullets, live ammunition and water cannons, resulting in numerous injuries."

During the protests, Kenya's parliament building and the president's office in the capital Nairobi were surrounded with razor wire, with all access roads blockaded by police. Thousands of protesters who were trying to access these sites clashed with police, who hurled tear gas canisters, fired live bullet rounds and wielded batons to keep them at bay.

Prior to the protests, Kenya's President William Ruto warned against disruption of peace and normalcy and called on Kenyans to support and respect police officers, calling them the most professional in the region.

"Nobody is above the law and you cannot intimidate the police," Ruto said.

"You cannot use force or insults against the police or threaten them, because you are threatening our nation. These are our frontline defenders."

Boniface Mwangi, a leading human rights activist, said that the protests were intended as a peaceful way of commemorating those killed a year ago. Regarding Wednesday's events, he lamented what he said was the unnecessary use of force by the government on protestors.