RIYADH (Reuters) - Saudi Arabia risks worsening already-tense relations with its Shia Muslim minority if it charges 16 detained Shias with spying in a case linked to rival Shia power Iran, community leaders said on Wednesday. The government has previously blamed unrest among Shias in the Qatif district of oil-producing Eastern Province on an unnamed foreign power, seen as code for Iran, a charge local activists have denied. Sixteen people have been killed in Qatif in clashes with police in the past two years. Shia activists said several members of their community had been arrested in the past four days across Saudi Arabia and their families had not been able to contact them.