AYENAT MERSIE PROTESTERS threw stones at police in Kenya's capital and attackers set fire to an office run by the president's party in a western town during a third wave of demonstrations organised by his opponents. Thousands joined marches called by opposition leader Raila Odinga against high living costs and alleged fraud in last year's vote. The government has said the vote was fair, defended its economic record and called for the protests to stop. Violence also marred Monday's protests, and the first demonstrations the Monday before that, prompting pleas for calm from civic leaders who said they feared a descent into…