An Iraqi Kurdish woman visits the grave of her sister, who was killed in a gas attack by former Iraqi president Saddam Hussein in 1988, during the 25th anniversary of the attack at the memorial site of the victims in the Kurdish town of Halabja, 300 kms (190 miles) northeast of Baghdad, on March 16, 2013. Many of those paying their respects held pictures of some of the estimated 5,000 people who were killed, most women and children, in what is now thought to have been the worst ever gas attack against civilians.