Authorities Friday considered even tighter security for Emperor Akihito's forthcoming coronation after two bombs blew up in a police dormitory, killing an officer and injuring six other people.

Following the blasts at the dormitory early Friday morning and late Thursday night, three unexploded bombs were found and a firebomb was hurled at a police station. There was no immediate claim of responsibility, but police said they suspected leftist radicals.The violence occurred as 26,000 police officers were mounting a massive security operation for the coronation Nov. 12. Representatives from more than 150 countries are to attend, including Vice President Dan Quayle and Britain's Prince Charles.