Tunisia troops kill gunman in polling station attack

TUNIS (Reuters) - One gunman was killed by Tunisian troops and three others arrested after they attacked a voting station late on Saturday, hours before polls opened for a presidential run-off, a defence ministry official said on Sunday. The gunmen opened fire from a car on a polling station in the central Kairouan governate, and troops shot back in response, the official said, without giving any more details. Security forces have been on high alert over a threat from Islamist militants to disrupt Sunday's presidential second round which marks the last step in Tunisia's transition to full democracy after the 2011 uprising against Zine El-Abidine Ben Ali.