Updated

By Alan Baldwin

LONDON (Reuters) - Formula One's season-opening Bahrain Grand Prix on March 13 may have to be called off due to civil unrest in the country, commercial supremo Bernie Ecclestone told Reuters on Thursday.

"We'll make a decision by Tuesday or Wednesday (next week)," he said.

"If it's not quietened down by Wednesday, I think we will have to cancel probably.

Ecclestone said he had spoken to Bahrain's Crown Prince earlier on Thursday for an update on the situation and would speak to him again on Friday.

"If you are making travel arrangements, I'd say don't," added the 80-year-old.

At least three people were killed overnight after Bahraini police stormed a protest camp in a central Manama square.

Thousands of overwhelmingly Shi'ite protesters have taken to Bahrain's streets this week demanding more say in the running of the Gulf Arab kingdom where a Sunni Muslim family rules over a majority Shi'ite population.

Two people died in demonstrations and clashes in Manama earlier in the week.

SAKHIR TESTING

A round of the GP2 Asia series scheduled to be held at the track this weekend was canceled earlier on Thursday due to the situation with circuit medical staff called to city hospitals.

Formula One teams are also due to test at Sakhir on March 3 after spending this week at Spain's Barcelona circuit.

Ecclestone said the calendar, with a record 20 races this year, would not be shuffled around if Bahrain was canceled and the Australian Grand Prix in Melbourne would therefore become the opener on its planned date of March 27.

"We may try to put it (Bahrain) on again later in the year," Ecclestone added.

Bahrain circuit authorities issued a statement later on Thursday assuring all potential visitors safety was a priority.

"Our focus at the present time remains on delivering another successful event," said circuit CEO Sheikh Salman bin Isa Al Khalifa. "We continue to monitor the situation very closely indeed in association with the relevant authorities.

"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."

(Reporting by Alan Baldwin, editing by Ken Ferris)