By James Pearson and Sohee Kim SEOUL (Reuters) - South Korean police clashed with thousands of protesters, blocking their way to the presidential palace, where they hoped to demand a more vigorous government response to a ferry disaster that claimed more than 300 lives a year ago. About 13,000 police and 470 police buses were deployed in the area around Seoul's main ceremonial thoroughfare and 100 protesters were arrested, an official of the Seoul Metropolitan Police Agency said. A fire department official said nine protesters and three police were taken to hospital while three protesters received first aid at the site.