A man walks on February 14, 2013 in a street of the city of Gao, northern Mali. Mali risks descending into "catastrophic" violence, the UN rights chief has warned, after a string of attacks by Islamist rebels increased the pressure on French-led forces in the west African nation. At right, a board with an inscription in homage to late French soldier Damien Boiteux, an helicopter pilot killed during the first days of the military operation in Mali.