LONDON, July 19 (Reuters) - Three British servicemen were killed on Thursday in a mortar attack on their base in the southern Iraqi city of Basra, the Ministry of Defence said. The deaths brought to 162 the total number of British servicemen and women killed in Iraq since the U.S.-led invasion in March 2003 to oust President Saddam Hussein. "It is with profound sadness that the Ministry of Defence must confirm the deaths of one serviceman from 504 Squadron Royal Auxiliary Air Force and two servicemen from 1 Squadron RAF Regiment on Thursday 19th July 2007," the ministry said. "They were killed in an indirect fire attack on the Contingency Operating Base in Basra," it said, adding that next of kin had been informed.