Nairobi - Kenya police used tear gas and water cannon on Friday on a large crowd of supporters of opposition leader Raila Odinga who gathered to welcome him from a trip overseas.Odinga had been speaking in the United States and Britain about Kenya's political turmoil following a court-nullified presidential election and the fresh vote last month. Odinga, whose claim of electoral fraud led the Supreme Court to nullify President Uhuru Kenyatta's re-election in August, boycotted the new vote, saying reforms had not been made.Kenyatta's win last month is being challenged at the Supreme Court by activists and a politician amid claims of irregularities. The court will make a decision on Monday.A police cordon ringed a park in Nairobi where Odinga was expected to address supporters. Police used tear gas on people walking in groups toward Uhuru Park.Youth who accused police of stopping them on a main highway from going to the airport to greet Odinga threw stones at officers. The confrontations were aired on live television.Rights activists condemned the police actions, accusing officers of taking sides in the political crisis and violating the constitution by preventing opposition supporters from assembling.The nullification of Kenya's August election was the first time a court in Africa had overturned a presidential vote. At least 70 people have died in political unrest since then, the majority opposition demonstrators shot by police during protests."In the face of this shameful police brutality and serious violations of human rights to life and physical security, the Uhuru Kenyatta government has remained mute and at times cheered the police on and made alarming statements in support of horrifying police actions," rights activist Ndungu Wainaina said.