UNITED NATIONS (AP) — Secretary-General Ban Ki-moon says he's concerned about reported clashes between security forces and demonstrators in Bahrain in recent days.

U.N. deputy spokesman Eduardo del Buey said Wednesday that Ban is calling on all parties to exercise maximum restraint, and for Bahraini officials to respect their international human rights obligations.

Bahraini Shiites are marking the one-year anniversary of their uprising against the country's Sunni rulers. Security forces fanned out across the island nation in unprecedented numbers, and police fired tear gas at protesters to pre-empt large demonstrations.

At least 40 people have been killed during a year of unprecedented political unrest in Bahrain.