Formula One world champion Jenson Button escaped unhurt from an attempted armed attack as he was driven away from the Brazilian Grand Prix circuit on Saturday, he and his McLaren team said.

The Briton, who won his title in Brazil a year ago, was in traffic outside the Interlagos circuit when a group of men with guns targeted his car.

"We were going back from the track and were outside a shanty town and moving slowly on a busy road," Button told the Mail on Sunday newspaper.

"I saw a dog come out, which was very cute. The next thing I saw was a man with a gun. I said, 'Isn't that a gun?', and as soon as I said that, the driver angled the car and floored it.

"That's when we saw six men, all of them brandishing machine guns."

McLaren said in an earlier statement that Button was quickly driven away from danger by an armed policeman trained in avoidance techniques who was at the wheel of the bullet-proof Mercedes provided by the team.

Button's father John, his manager Richard Goddard and physiotherapist Mike Collier were also in the car.

Goddard told Reuters that they had left the circuit at 1900 local (2100 GMT) and were stationary in a queue of cars when they spotted a group of men running out of a building to their right.

"I noticed one of the guys had what looked like a big truncheon and then someone shouted, 'One of them has got a gun'," he said. "And another one seemed to have a much bigger weapon.

"The guy pulled the gun out and someone else pulled an even bigger one out and they came running over towards the car. We told the driver, 'go, go, go'."

The driver hit several other cars as he forced his way through the traffic to safety, Goddard said.

"Thankfully the Merc was bloody strong and we had a police driver. If we hadn't it would have been potentially a very nasty situation ... they certainly weren't carrying handguns," he said.

"I don't know what would have happened if he hadn't got the car out."

McLaren said the Sao Paulo authorities would provide additional security to transfer the drivers and other senior team personnel to the circuit for Sunday's penultimate race of the season.

Although the area around Interlagos has become more built up over the years there are still favelas, or shanty towns, in the vicinity, while Sao Paulo is a sprawling city with one of the highest crime rates in South America.

Teams are always on the watch for attempted armed attacks on members leaving the circuit after previous incidents over the years despite a strong police presence.

Members of the Toyota team were ambushed at gunpoint four years ago as they left the circuit, with shots fired by a gang of youths who also tried to kick in their car windows. None suffered any injury.

Goddard said he had noticed a group of about 70 policemen being talked to by an officer less than 200 meters further up the hill from the incident.

Button had earlier qualified 11th on the starting grid, with his four title rivals well ahead of him and his hopes of retaining the title are likely to be extinguished on Sunday.

"Before, there was a sliver of hope of retaining the championship, but now it's gone. It's basically impossible," the Briton had told reporters.