Tributes have poured in for two Scottish soldiers killed in Afghanistan as a major British offensive in the country looms.

Relatives of Corporal John Moore, 22, from Bellshill, Lanarkshire, and Private Sean McDonald, 26, who was born in Toronto but went to school in Edinburgh, spoke of their "devastation" after the pair were killed by an explosion on Sunday.

The tributes were paid as defence sources said the heavily-trailed Operation Moshtarak was reaching the final "shaping phase". British forces are joining Afghan and US allies in rooting out Taliban insurgents from their stronghold in the town of Marjah in Helmand province.

Cpl Moore and Pte McDonald were "professional, courageous, selfless, and committed - true infantry soldiers", Defence Secretary Bob Ainsworth said.

Cpl Moore, from the Royal Scots Borderers, 1st Battalion The Royal Regiment of Scotland, was commanding his section on a routine night patrol when a roadside bomb detonated, killing him and Pte McDonald.

Mr Ainsworth added: "Hearing about these two brave men, I am filled with admiration for their courage and loyalty."

A statement from Cpl Moore's family said: "Johnathan was a proud Scottish soldier who was doing a job that he loved - he will be sadly missed by a loving and very proud family. The Army and his family were Johnathan's life we are devastated at our loss."

Pte McDonald, who had a wife, Jennifer, will be "desperately missed", his mother Jacqueline McDonald said. "My son was so proud to be a soldier. This tragedy has left a hole in our lives and a hole in our heart. Sleep well baby boy."

Operation Moshtarak is expected to start in the coming days.

Mr Ainsworth has warned of a "very real risk" that British lives will be lost during the fighting to come.