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A lower-tier open-wheel race in Bahrain was called off Thursday amid anti-government protests and a crushing response by riot police. The cancellation leaves in doubt next month's season-opening Formula One race at the same track.

The Bahrain Grand Prix is scheduled for March 13, with F1 workers due in the country 10 days earlier.

Formula One chief Bernie Ecclestone said he will wait until next week to decide whether to proceed with the race. He spoke Thursday to Crown Prince Sheik Salman bin Hamad Al Khalifa about the situation.

"It's not good is it?" Ecclestone said. "We'll have to keep our eye on things and make a decision quickly. I spoke to the crown prince this morning. He doesn't know any more than you or I, but they're monitoring exactly what is going on."

Organizers said the GP2 Asia Series race set for Friday and Saturday was canceled at the request of the Bahrain Motorsport Federation because of "force majeure" — a French expression referring to uncontrollable events. No further information was available.

FIA, the governing body of motor sports, has expressed confidence that the protests on the island nation in the Gulf would not prevent the running of next month's F1 race.

"We are constantly in touch with both the national authorities and local authorities," FIA spokesman Norman Howell said. "We are monitoring the situation."

Shaikh Salman bin Isa Al Khalifa, chief executive officer of the Bahrain International Circuit, has said security remains of paramount concern.

"Our priority at this time is ensuring the well-being of everyone associated with this event, and we will respond appropriately to any further developments," he said in a statement.

Riot police with tear gas and clubs early Thursday broke up a camp that anti-government protesters had set up on the square, killing four people, according to medical officials. Armed patrols prowled neighborhoods throughout the day and tanks appeared in the streets for the first time. Public gatherings were banned Thursday and the city was virtually locked down.

Bahrain's King Hamad bin Isa Al Khalifa made a rare national TV address, offering condolences for the deaths, pledging an investigation into the killings and promising to push ahead with reforms.

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Associated Press writer Hadeel Al-Shalchi contributed to this story from Manama, Bahrain.