* Armed robbery committed when most of accused were juveniles
* Amnesty says "confessions" were beaten out of defendants
* Saudi Arabia criticised in West for high rate of executions (updates with further extension of stay of execution)
RIYADH, March 5 (Reuters) - Saudi Arabia has granted a last-minute stay of execution to seven men who were due to die on Tuesday for their part in an armed robbery committed when most of them were juveniles, relatives and family friends said on Tuesday.
The seven were sentenced to death in 2009 for robbing a jewellery store in the southern province of Asir in 2006, but Amnesty International quoted the men as saying they were tortured into confessing.
It was the latest case to focus the spotlight on the Saudi legal system, which is based on a strict version of Islamic law, or sharia.
The kingdom has been criticised in the West for its high number of executions, inconsistencies in the application of the law and its use of public beheadings.
A spokesman for Saudi Arabia's interior ministry was not immediately able to comment on the case. The Riyadh government has repeatedly denied that the kingdom practices torture.
Mohammed al-Rabhan, a family friend of some of the convicts, said King Abdullah's eldest son, who commands the Saudi Arabian National Guard, on Tuesday ordered a one-month stay of execution while the royal court looked into a request for a retrial.
"Prince Miteb also promised those who met him to order a new investigation and a new trial, commute the death essence or even pardon them," Rabhan added by telephone after he and about 200 other relatives and friends of the young men had gathered near the king's court to appeal for clemency.
Friends and family members said news of the prince's order came soon after the governor of Asir province ordered a 10-day delay to the execution, originally scheduled for 9 a.m. (0600 GMT) on Tuesday.
Dheeb al-Qahtani, a brother of one of the convicted men, thanked the Asir governor for delaying the execution.
"We hope that Abu Miteb (King Abdullah) would order their release," he told Reuters by telephone.
Amnesty said the men had been "severely beaten, denied food and water, deprived of sleep, forced to remain standing for 24 hours and then forced to sign 'confessions'".
Rabhan said that the men were coerced into confessions and said the men were adolescents, aged between 15 and 18 at the time of the robbery who did not realise the implications of their actions.
"The investigation was marred by many violations that distorted the trial," he told Reuters by telephone. "We are not saying that they are not guilty. We are saying these crimes do not deserve the death penalty."
Relatives and friends said 30 people were tried for a series of crimes, including a string of robberies of jewellery stores in the area. Seven were sentenced to death, while the rest were given prison sentences or acquitted.
The seven are from Asir, one of the least developed parts of the kingdom that is the world's top oil exporter.
The last time the kingdom executed so many people at once was in October 2011, when eight Bangladeshi men were put to death for an armed robbery in which a guard was killed.
Saudi Arabia has executed 17 people so far this year, said Amnesty, compared to 82 in 2011 and a similar number last year.
Capital crimes resulting in the death sentence last year included murder, armed robbery, drug smuggling, sorcery and witchcraft. (Reporting By Sami Aboudi; Editing by Angus McDowall and Andrew Heavens)