CHICAGO (CBS) — President Obama has arrived in Chicago for the two-day NATO summit that is being held in his hometown amid protests by demonstrators.

Air Force One touched down at O’Hare International Airport shortly before 8:30 p.m. Saturday, hours after the president concluded the G8 conference at Camp David. Obama and his wife, Michelle, were greeted by Mayor Emanuel, the president’s former White House chief of staff.

City officials earlier Saturday said Columbus Drive would be closed between Illinois Street and Wacker Drive, presumably for security reasons connected with the two-day NATO conference, which concludes Monday. More than 50 heads of state are attending the summit at McCormick Place, and a large section of Lake Shore Drive has been closed, also for security reasons.

A major issue for NATO members is security in Afghanistan, and the international organization’s military policies have sparked protests across Chicago in the days leading up to summit. Police have made a relative handful of arrests as demonstrators have held marches and at times shut down traffic.

The latest confrontations took place Saturday evening as the president was arriving.