Extremists who promote terrorism on social media can expect "heavy" prison sentences, leading judges have warned.

Emphasising that the dissemination of terrorist material can have "serious consequences for innocent people", they threw out a sentence challenge by an "extremist" mother-of-six at the Court of Appeal in London.

Runa Khan, 35, from Luton, Bedfordshire, who promoted terrorism on Facebook, was jailed for five years and three months at Kingston Crown Court in Surrey in December.

Khan revealed her radical views on the social network, encouraging fellow Muslim women to urge their male relatives to fight and posting a picture of a suicide vest.

She also praised an article giving tips on how to prepare young children for jihad and unwittingly passed a route to Syria to an undercover police officer.

When she was arrested police found a photo of her two-year-old son with a toy assault rifle on her phone, as well as images of her and her older children holding a sword.

Khan, who admitted four charges of disseminating terrorist publications between July and September 2013, watched today's appeal proceedings via video-link from prison.

Her bid for a reduction in her sentence was rejected by Lord Justice Laws, Mr Justice Blair and Mr Justice Holroyde.

Announcing the decision of the court, Mr Justice Blair said: "It is evident from her online activities that it is fair to describe her as someone who holds extreme Islamist views."

He said: "It is accepted that the appellant has suffered many difficulties in her life, not least her current ill health. There is mitigation in her case and the references the court has read testify to the positive elements in her character."

Ruling that the appeal "must be dismissed", he said: "What makes these offences particularly serious in our view is what the judge (sentencing judge) describes as the appellant's deep commitment to the radicalisation of children, including very young children, into violent jihadist activities."

He concluded: "Offences of this kind can have serious consequences for innocent people and are bound to attract a heavy sentence."