KARACHI (Reuters) - Pakistans foreign exchange reserves fell to $15.71 billion in the week ending June 11, down from $15.87b the previous week, the State Bank of Pakistan said on Thursday. Reserves held by the State Bank of Pakistan (SBP) fell to $11.97 billion from $12.14 billion a week earlier, while those held by commercial banks rose to $3.74b from $3.73 billion, said the State Bank of Pakistan. Last month Pakistan received $1.13 billion as the fifth tranche of a $10.66 billion Int'l Monetary Fund (IMF) loan. The Int'l Monetary Fund loan package was agreed to in November 2008 to help avert a balance of payments crisis and shore up reserves. Pakistans foreign reserves hit a record high of $16.5 billion in October 2007 but fell steadily to $6.6 billion by November 2008, largely because of a soaring import bill.