The Catalan government has called for tougher penalties for violent crimes after a surge in knife attacks and violent robberies in Barcelona.

Miquel Buch, the regional interior minister, said the law needed to be changed after it emerged that 90% of those charged with violence in recent months had been released on bail.

Though Barcelona has long been notorious for its pickpockets and bag snatchers these incidents seldom involved violence. However, police officials say there have been 5,331 violent street robberies so far this year, a 30% increase on 2018. Shopkeepers have also reported a sharp rise in violent robberies.

Knives have been used in at least 100 crimes, including robbery, fights and homicide, although police say they have not confiscated more knives than usual.

In June, a South Korean woman who was part of a government advisory body died from head injuries after she fell during an attack by muggers. On Sunday, the Afghan ambassador to Spain, Humayoon Rasaw, was attacked in central Barcelona and his €17,000 (£15,000) watch stolen.

Critics of the justice system say many thieves operate with impunity because of a law stating that the theft of property worth less than €400 is a misdemeanour, not a crime. This means many thieves receive only a fine no matter how many times they reoffend.

The use of violence is a crime, however, but police say of the 1,529 people charged with such offences, only 165 have been remanded in custody.

Despite assurances by the Barcelona mayor, Ada Colau, that the city is safe “but has some security problems”, the US embassy has advised its citizens to beware of the risks of visiting Barcelona.

The issue has led some people to blame Colau, immigrants and the law.

Some say the rise in violent crime is due to the influx of unaccompanied minors, young boys mostly from Morocco, of whom more than 6,000 have arrived in the city in the past two years and for whom there are few facilities. However, police say the overwhelming majority were not involved in criminal activity.

Police and legal experts are at a loss to explain why many of the non-violent thieves who have operated in the city for years are now using force.

Violent crime reached a similar peak in the summer of 2012, but declined steadily until 2016 before rising again.

The main factor appears to be a surge in tourism, with many visitors proving to be easy pickings for thieves.

Ciutat Vella, the old part of the city that attracts the most tourists, has the highest level of street robberies. In the past year there has also been an increase in gangs forcibly stealing expensive watches.