LIVERPOOL, England (AP) _ Britain's famed Grand National Steeplechase, along with today's entire card at Aintree racecourse, was called off because of a bomb warning that proved more than a threat. Police found and exploded two devices.

All 60,000 spectators, including Princess Anne, were evacuated because of two coded warnings received by police.

Evacuation of the main grandstand began a half hour before the scheduled start of the race. And, at the precise moment the 4 1/2-mile steeplechase was due to go off, officials announced the entire track would be cleared and racing called off.

``We are going to evacuate the whole course. There is no possibility of racing and we are going to abandon racing for the day,'' said clerk of the course Charlie Barnett

Prime minister John Major blamed the IRA for the incident. A week ago the IRA planted bombs near railway lines some some 30 miles south of Liverpool and more devices were found at crossroads further south at Birmingham.

``I am appalled that the IRA seem to be threatening hundreds of thousands of people and causing such disruption,'' he said.

``This is further demonstration of their contempt and disregard for the lives and interests of ordinary people. The IRA's campaign is cynical and detestable.

``They must know that this can only harden our resolve never to make concessions to terrorists.''

However, trainer Jenny Pitman believed the threats were the work of animal rights activists, who have tried to disrupt the race in the past.

``I'm afraid these people are very sick. If you could have just seen the scenes down the stableyard where we have had to leave our horses,'' said Pitman, who has trained two winners of the prestigious race.

``They just said `You've got to leave your horses and get out of here','' she told the BBC.

``I just find that anybody involved in such a disgusting act is unbelievable,'' she said of the bomb warning. ``Don't tell me these people love horses, love animals. don't tell me they are in any way human because they are not.

``We won't give into them.''

Actor Gregory Peck, celebrating his 81st birthday, also was among celebrities evacuated from the stands.

The 38 horses were already parading when police told organizers that two coded bomb warnings had been received.

Unprecedented security was in operation anyway after the discovery last week of the explosive devices.

Some 500 police, some with flak-jackets and carrying semi-automatic weapons were on duty for the first time in the 158-year history of the famous steeplechase.