By Ian Youngs BBC News Online entertainment staff

The Scream thieves were caught on camera making their escape

The theft has highlighted gaps in the insurance of major works around the world, with a large number not covered against being stolen, according to some of the UK's leading art insurers.

Many galleries and collectors cannot afford to pay for protection or do not think they will need it, Adam Golder, chief executive of Axa Art UK, told BBC News Online.

"Quite a lot of the world's art, believe it or not, is not insured, or is insured only for that which a budget constraint will allow," he said.

"This is a good wake-up call to really look at what they are covered for."

Robert Graham, insurance broker with Blackwall Green, said: "Often they're not insured at all.

"If they're in national museum collections or regional museum collections, they simply don't have the finances to pay for insurance."

They are not replaceable so you can't buy The Scream on the street and put a copy up there John Oyaas Oslo Forsikring insurers

But most important private collections usually had full insurance, he said.

The Scream, which was taken by two armed men from the Munch Museum in the Norwegian capital, was insured against water and fire damage - but not theft.

Its insurers say this is because if a painting is damaged by smoke or flooding, the gallery needs money to repair it.

But if a painting is stolen, the gallery cannot simply go out and buy another copy with the insurance money.

"They are not replaceable so you can't buy The Scream on the street and put a copy up there," said John Oyaas, managing director of the museum's insurers, Oslo Forsikring.

"The focus is on other issues than insuring them. To a certain extent this is common practice because these items aren't replaceable."

The frames of the Munch paintings were found in the street

But if a painting is stolen, damaged then recovered - and The Scream is very fragile - there will be no insurance money for repair.

In the UK, the famous and valuable works in the permanent collections of national institutions such as the Tate and National Gallery are not insured at all.

Government-funded institutions are forbidden from taking out commercial insurance for their permanent collections, with a special government scheme to cover items on loan.

"Items in a national museum's permanent collection are already ultimately owned by the government and the people of this nation," a spokeswoman for the Department for Culture, Media and Sport said.

"They've been bought with taxpayers' money or given to the nation.

"Those items are not insured - they are not insured commercially largely due to cost, and how you would put a value on what's in the national collections?"

The standards here in terms of security are exceptionally high Department for Culture, Media and Sport spokeswoman on UK national galleries

If those items are lost or damaged, the galleries can request money from the government for repair or replacement.

That "almost never" happens, she said, adding that the government could not provide formal cover because it already officially owns the artworks.

"The standards here in terms of security are exceptionally high," she added.

Mr Graham said if items were not insured, most galleries made sure the chance of a theft was very low.

"That's what a lot of museums do - rather than spending money on insurance they'll spend money on risk management.

Trustworthy

That would include "very strong physical security and a lot of manpower" so the theft did not happen in the first place, he said.

Security is one of the main factors when insurers work out much art owners should pay in premiums - along with who the owner is and how trustworthy they are.

Theft insurance would not usually add a huge amount to fire and water cover, according to Mr Golder - unless the security was not considered to be up to scratch.

And insurers would rarely refuse to protect an item, he said.