The ruling coalition on Friday began deliberations in the Diet on a contentious bill to revise the Upper House electoral system after a violent confrontation with the boycotting opposition, whose members tried to block the door to a committee meeting room.

With the Diet boycott in its fifth day, the ruling bloc sent the bill to an Upper House special committee where deliberations commenced immediately without the opposition represented.

The situation turned violent earlier in the day as opposition lawmakers attempted to prevent members of the ruling bloc from attending a meeting of an Upper House steering committee to set the day's Diet proceedings.