BEIRUT - Syria's political opposition in exile urged all Arab countries on Monday to sever diplomatic ties with Iran after Saudi Arabia, a strong supporter of the Syrian opposition, cut relations with Tehran. Saudi Arabia has been rallying Sunni allies to its side in a growing diplomatic row with Iran, deepening a sectarian split across the Middle East following its execution of a prominent Shi'ite cleric. The Turkey-based Syrian National Coalition declared its support for Riyadh's move, calling on 'all Arab and Islamic countries to take a similar step' and criticised what it said was Iran's support for militias in Syria and Iraq.