A border police guard and three civilians were injured when Iranian forces shelled an Afghan security post in southwestern Nimroz province, an official said on Tuesday. The cross-border attack came after Afghan police stopped Iranians from diverting water from the Sikhzar canal on Monday, said the provincial border police chief, , Col. Ghulam Haidar. The 30-kilometre canal, located inside Afghanistan, was built last year at a cost of $700,000 (32 million afghanis) provided by the United States Agency for International Development (USAID).