One woman was killed and five other people were injured by a man with a knife in central London in an attack which police said could be linked to terrorism. Police said they had been called shortly before midnight after the man had injured several people in London's Russell Square. Police used a Taser gun while arresting the man. 'Terrorism is one possibility being explored at this stage,' police said in a statement. A woman was treated at the scene but was pronounced dead a short time later, police said.