Stolen: Detail of Jeune Parisienne by Renoir

Reports say he and another lawyer detained earlier are suspected of acting as go-betweens with the thieves in their efforts to obtain a ransom for the pictures.

The missing paintings - estimated to be worth up to $30m in total - were stolen in December by three armed men in what has been described as the most audacious art theft in Swedish history.

Ransom

The latest arrests bring to eight the number of those detained in the case - seven Swedes and one Russian.

The Swedish newspaper Expressen said a 42-year-old Russian was thought to have masterminded the operation. He is said to have connections with criminal networks abroad.

Stolen: Rembrandt self portrait from 1630

Reports say one suspect is being held on charges of extortion, and another for allegedly receiving stolen goods.

The two lawyers are presumed to have acted as intermediaries between the police and the gang, which several hundred thousand dollars for the paintings. Police have insisted no money will be paid.

All the suspects' names have been withheld following Swedish court procedure.

Boat escape

On 22 December three masked raiders walked into the museum in central Stockholm as it was preparing to close for the day.

Stolen: Detail of Conversation with the Gardener by Renoir

One, armed with a machine gun, held up security staff while the other two ran to different rooms upstairs.

After ordering guards there at gunpoint onto the ground, the two thieves went straight for their target paintings. Within moments all three had left the building and sped off into the darkness on a small motor boat waiting for them near the museum.

The works stolen were: Self Portrait (1630) by Rembrandt, and two paintings by Renoir - Conversation with the Gardener and Jeune Parisienne. They were each valued at between $7.5m and $10m.

None of the paintings was insured.