MOSCOW, March 23 (Xinhua) -- Russian President Vladimir Putin said Saturday all four gunmen in the Moscow terrorist attack were arrested. Putin, addressing the nation, said that all those responsible for the deadly attack would be punished. He also ordered that Sunday will be a nationwide day of mourning. A deadly shooting at a concert hall in suburban Moscow Friday killed at least 143 people and injured over 100, local authorities said. 

（Editor:Liao Yifan）