Gun attacks in Europe
As more details emerge of the shooting spree and grenade attack in Belgium in which five people died, the BBC News website takes a look at other recent incidents in Europe - and the effect they have had on each country's laws.
Seventy-seven people were killed in twin attacks on 22 July 2011 in Norway. Anders Behring Breivik has admitted that he planted a car bomb that exploded close to government offices in the capital Oslo, killing eight people. He then drove to the island of Utoeya, where a summer camp for the governing Labour Party's youth wing was being held, and shot dead 69 people, most of them teenagers.
Breivik has been declared a paranoid schizophrenic after months of assessment and is more likely to be detained in a mental institute rather than prison. In a 1,500 page manifesto, he outlined his radical right-wing views and the steps he took to obtain powerful guns - including joining a firearms club in 2005 to increase his chances to obtain a Glock 17 semi-automatic pistol six years later.
Norway has restrictions on gun ownership but hunting is popular. Breivik wrote in his application for a licence to own a semi-automatic weapon that he needed the gun to hunt deer.
In the aftermath of the attacks Norway's police chief, Oeystein Maeland, said that he wanted a tightening of the laws on semi-automatic weapon ownership.
A committee established by the Norwegian Justice Department to investigate the country's gun controls has recommended a new law with greater emphasis on safety and preventative measures. Suggestions include regular monitoring of licensed gun owners and checking with household members of applicants that they are aware of the application.
In April 2011 a gunman killed six people at a shopping centre in Alphen aan den Rijn using an automatic weapon. The attacker, Tristan van der Vlis, later killed himself. He was a member of a local gun club and legally owned three guns - despite having previously been a resident at a psychiatric institution.
The Netherlands has low levels of gun ownership and relatively strict firearms laws. Applicants for a licence must prove that they have a genuine reason to want a gun, such as hunting, being a sports shooter or a collector. They must pass background checks and re-apply every year.
In September Radio Netherlands Worldwide reported that the Dutch security and justice minister planned to ban semi-automatic rifles, saying it was "unacceptable for members of a shooting club to have such a weapon, let alone keep one at home".
A gunman killed 12 people and injured 11 on a rampage in Cumbria in north-west England in June 2010.
Taxi driver Derrick Bird shot dead a colleague in the town of Whitehaven, before driving through the countryside apparently targeting people at random.
The 52-year-old used legally held firearms but had received a suspended sentence for theft 20 years earlier.
In September 2011 the Home Office, reviewing recommendations from a committee of MPs in the wake of the attack, said it would update guidance rather than making any new laws. It indicated that in future it might be that someone who had been given a suspended sentence would be refused a firearms licence.
Gun laws were significantly tightened in Britain following the massacres in Hungerford in 1987 and in Dunblane in 1996.
Fifteen people plus the gunman died in a shooting spree by a teenager in south-west Germany in March 2009. The 17-year-old killed nine pupils and three teachers at his former school in Winnenden, then three more people after leaving the premises. The gunman's father was later convicted of breaking Germany's gun laws as his legally held weapons (one of which was used by his son) were not stored securely.
In April 2002 a former student at a school in Erfurt killed 16 people then himself.
German laws were tightened after the Erfurt massacre, increasing the minimum age for purchasing guns from 18 to 21, banning pistol-grip shotguns and outlawing certain types of knives. In July 2009, following the deaths in Winnenden, they were amended to allow routine checks on storage for firearms at licence holders' homes.
In September 2008 a 22-year-old student shot 10 people at a college in the town of Kauhajoki before turning the gun on himself. It was less than a year after an attack at Jokela High School in which seven students, a teacher and the gunman died.
Finnish gun laws were among the most relaxed in Europe, and in 2007 the interior ministry said there were 1.6 million licensed firearms for its population of just over five million people. Most of these licences are issued for hunting which is a popular sport in Finland.
In June 2011 new laws came into force which raised the minimum age for a handgun licence to 20, introduced an risk assessment test for would-be gun owners, and restricted the availability of handguns.
In 2001, a disgruntled local man shot dead 14 people in the Swiss town of Zug. Friedrich Leibacher, 57, burst into a session of the local assembly disguised as a police officer and opened fire.
Switzerland has a high rate of gun ownership as Swiss men keep their army gun at home after they finish compulsory military service. No-one knows the exact number of guns as there is no national register but it is estimated that there are two to three million firearms in the country, which has a population of seven million.
Voters rejected proposed tighter controls on gun ownership in a referendum in April 2011.