Opposition coalition chief executive officer Norman Magaya said that police have allowed government supporters into the banned protest areas and that they were attacking opposition supporters.
Two protesters killed in Bondo as demonstrators clash with police in rally calling for reform of electoral commission.
Odinga's decision to withdraw from the upcoming vote has renewed fears of political violence; 17 were injured last Wednesday while protesting President Uhuru Kenyatta's rejection of electoral reforms.
The demonstrations defied a new government ban on opposition protests in the central business districts of Kenya's three largest cities, while concerns rose again about election-related violence in East Africa's largest economy. In Kisumu city, local television showed running battles with stone-throwing youth.
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Police in Kenya's three largest cities also used tear gas Friday on opposition demonstrations that defied a government ban and pressed for electoral reforms ahead of fresh presidential elections on October 26.
The Supreme Court said a new election must take place within 60 days, and Odinga has demanded fundamental reforms such as the sacking of top IEBC officials and the recruitment of new companies to print ballot papers and run election technology.
Kenyatta and Odinga were due to return to the polls because the Supreme Court nullified Kenyatta's win in an August 8 election, citing procedural irregularities.
The opposition leader said he could return to the Supreme Court to seek a clarification, but if the IEBC went ahead with the October 26 election it would be "in breach of the law".
The opposition view is that a 2013 ruling by the Supreme Court means if any candidate withdraws, the IEBC must conduct fresh poll nominations, beginning the whole process over again. On Wednesday Kenya's national assembly - dominated by the ruling Jubilee party - approved a series of electoral law changes that Odinga has argued will make the "irregularities" cited by the Supreme Court, legal. Human rights groups protested, with some pointing out that police have killed at least 37 people in demonstrations since the results of the August election were announced.