A murderer and a robber who sent crude explosive devices from the segregation unit of a top security jail to Asian solicitors as part of a race-hate campaign have had their prison sentences increased.

Bret Atkins, 24, and Jamie Snow, 27, smirked and laughed today as a judge at Leeds Crown Court was told how they constructed basic incendiary devices made from crushed match heads in their cells at Full Sutton prison, near York, and sent them to law firms in Halifax and Nottingham.

Despite Atkins and Snow appearing by videolink from different prisons - Whitemoor and Wakefield - the two managed to exchange smiles with each other as details of their racist messages were read to the court.

Atkins - who is serving a life term with a minimum term of 20 years for murdering a man in Hull in 2009 - grinned even though his barrister told the judge he had converted to Islam since arriving at Whitemoor.

Today, Judge Rodney Jameson handed down a seven year prison sentence to Atkins, who was found guilty by a jury earlier this year of conspiracy to send an explosive substance with intent to burn.

The judge ordered this to start 18 months before the end of his current 20 year minimum term and said this would have the effect of increasing the minimum term of his life sentence to 22 years.

Snow, who is originally from Leeds, was serving an eight-and-a-half year sentence for robbery, attempted robbery and possessing a firearm with intent when he sent the letters.

He was given an extended sentence of six years and three months today after admitting offences of sending an explosive substance with intent to burn and making threats to kill. The judge said the extended part of the sentence meant he will be on licence five years after he is released.

Atkins admitted murdering 35-year-old Simon Ash in Hull in 2009.

A judge at the time said he and another man had "callously and cold-bloodedly" killed Mr Ash, who was walking alone.

They kicked him and stamped on his head so hard that an imprint of Atkins's shoe was left on his face.