AK-47s, sub-machineguns, even rocket launchers used by Islamist terrorists last week - and they're easier to buy than you think.

The weapons wielded by gunmen sowing mayhem at Charlie Hebdo magazine and a Jewish supermarket in Paris this week were powerful but - for those in the know - readily available in France, experts say.

Kalashnikov assault rifles, the M82 grenade launcher, hand grenades, explosive material, Tokarev handguns: everything in the arsenals possessed by the Koubachi brothers and Amedy Coulibaly would be available from the same sources supplying urban crime gangs.

"Unfortunately these types of military weapons have been available for a long time and one can get them without attracting attention," an anti-terrorism official who asked not to be identified told AFP.

"Look at people who rob armored bank vans. They've long been able to get explosives, military Semtex, heavy weapons and rocket launchers. They also know how to use them," he said.

An expert in arms trafficking in France, who also wanted to remain anonymous, said Coulibaly, who took hostages at a supermarket on Friday and killed four before being gunned down by anti-terrorist police, had a "very easily" available weapon.

"Coulibaly had a Czech-made Scorpion sub-machinegun. It's been around for 30 years on the grey market. It's sought after by drug traffickers because of its small size and firepower. As for the Kalashnikov, it's even easier to get," he said.

Yugoslav-manufactured AK-47 Kalashnikovs have been available throughout western Europe since the fall of the communist regime in Albania and the break-up of Yugoslavia. The going price on the black market is between 1,000 and 2,000 euros ($1,300 and $2,600), depending on its condition, while a Scorpion costs about 1,500 euros, and a grenade launcher with ammunition goes for about 2,000 euros.

Rocket launchers no harder

"It's small-scale trade, two or three Kalashnikovs at a time hidden in the boot of a truck going between Bosnia or Serbia. There's no network or supply line that the police can infiltrate," the expert said. "It's no harder with rocket-launchers. They also come from the east and the big gangs hitting bank vans have used them for a long time."

Explosives brought by Coulibaly to the supermarket were never used. These were of civilian grade, for example the type used in mines, and are often stolen.

Jean-Charles Antoine, at the French Institute of Geopolitics and author of the book "At the Heart of Arms Trafficking", said the intelligence services are unlikely to pick up on these kinds of weapons purchases, unless the assailants buy everything at once.

"But that would be especially stupid," he said.

"Most probably they bought everything in stages through intermediaries and built up their little arsenal bit by bit, some here, some there," he said.

The sellers may not have known what the weapons would be used for, but in any case, "among these people - arms traffickers and organised criminals - they rarely call the police to warn 'a cell is being formed'."