Dozens of fighter jets and other warplanes soared over Beijing on Monday as China stepped up preparations for the 60th anniversary of communist rule, tightening security with restrictions on knife sales and plans to ground flights on Oct. 1.

The planes and helicopters flew in formation over Chang An Avenue, the major boulevard that runs east-west through the city and across the top of Tiananmen Square. Some of the planes released streams of red, blue and yellow smoke as they flew low over the city in a rehearsal for the National Day celebrations.

China has tightened security in recent weeks ahead of the holiday. In the latest move, sales of knives have been banned at some stores including large retailers such as Wal-Mart and Carrefour, after two separate knife attacks near Tiananmen Square last week, according to store officials and state media.

A spokesman surnamed Wang for Wal-Mart in Beijing said police inspected the stores on Sunday and asked them to remove all knives from their shelves until further notice.

The fly-over comes after camouflaged tanks, trucks bearing intercontinental ballistic missiles and parade floats rumbled down the city's main street on Friday in a full dress rehearsal. All offices, shops and restaurants were closed along the routes, with hundreds of tactical police units with automatic rifles and paramilitary police lining the thoroughfares.

Authorities plan to ground flights into and out of Beijing for three hours during the parade on Oct. 1, according to a ticket agent, who refused to give her name, at the Beijing Capital International Airport. State media also reported the flight restrictions, which are similar to ones in place for last year's Beijing Olympics.

Few details have been given on the schedule for the celebrations, but a keynote address from President Hu Jintao is expected, followed by an elaborate military parade and performances involving 200,000 people, 60 floats and fireworks.