A "substantial" reward has been offered after thieves stole five paintings by LS Lowry in a haul worth more than a million pounds from a private collection.

The Lowry works - valued at up to £250,000 each - were among a collection of some 59 paintings taken two weeks ago from premises in Northamptonshire where they were being stored by their owner.

Auction houses around Europe and Interpol have been alerted and advertisements have been placed in antique trade publications to warn dealers.

And a reward - believed to be a five-figure sum - has been offered to help recover the artworks. The owner of the paintings has asked for no publicity.

The stolen Lowry paintings are Gateposts in the Snow, The Chapel, A Cornershop, People on a Promenade and Street Scene.

Most of rest are 18th and 19th Century works, many of them by skilled amateur English artists.

'Significant loss'

Laurence Stephen Lowry, who died in 1976, based most of his work on working-class street scenes featuring his famous "matchstick" figures, in and around his native Salford, near Manchester.

Last December a painting of a football match by LS Lowry was bought for a record £1.9m by the Professional Footballers' Association (PFA).

The players' union bought the 1953 picture, Going To The Match, at Sotheby's auction house in London, setting a record price at auction for any modern British painting.

Fine art loss adjuster Mark Dalrymple said: "It's a significant loss to the art world, but is hopefully a temporary loss.

"We have alerted the trade and placed details with the police and on computer databases, so these people are not going to get a very good price if they try to sell them on."