TEHRAN — Iranian authorities said they dismantled four terrorist cells and arrested 16 people in the southeastern province of Sistan and Baluchestan, the province's intelligence department announced Tuesday. The operation took place in central and southern parts of the province, which borders Pakistan and Afghanistan, according to a statement carried by the Mehr News Agency (MNA). The intelligence department said some of those detained had entered Iran from abroad, though it did not specify their nationalities or the countries they came from.