The 30-year-old Serb, who has no existing criminal record, had burst into the jewellery shop on the C/ Ayala, in the Salamanca district, together with an accomplice.

Both were armed with knives and squirted pepper spray in the owner's eyes.

But the owner was too quick for them and fired a volley of shots, several of which hit one of the men in the chest and groin.

The chest wounds were superficial, but the shot in the groin was near the femoral artery and may have penetrated it.

Witnesses say the injured man tried to get in a taxi, but that the driver insisted on calling the police when he saw that he was covered in blood.

The Serb continued walking for a few steps, but then collapsed unconscious.

Emergency services found him lying on the pavement and he was taken to La Paz hospital in the city, where his condition is said to be critical.

And the shop owner was taken to La Princesa hospital to be treated for the pepper spray in his eyes.

It is not known whether he will be charged for the shoot-out, or whether it will be considered that he acted in self-defence.