By Angus McDowall
BEIRUT (Reuters) - A Lebanese military court on Friday increased to nearly 10 years the jail term for a former minister convicted last year of smuggling explosives and planning attacks, in a case that has underscored the country's sharp political divisions.
Former information minister Michel Samaha, who has close ties to Syrian President Bashar al-Assad, was detained in August 2012 and confessed to involvement in a plot for which Damascus' security chief Ali Mamluk was also indicted.
Syrian officials have denied Damascus was involved, but the allegations exposed rifts in Lebanon, which often break along sectarian lines, over Syria's long-standing involvement in the country.
Samaha's initial four-year sentence and later release on bail prompted bitter protests from opponents of Assad, who saw the decisions as unduly lenient and evidence that Damascus and its ally Hezbollah held sway over the justice system.
The case also gained wider regional significance when Saudi Foreign Minister Adel al-Jubeir suggested it was part of the reason Riyadh was withdrawing billions of dollars in aid from Lebanon's army and security forces.
He said the military court's granting of bail to Samaha raised questions over the army's independence from the Shi'ite Hezbollah movement, Lebanon's main powerbroker and a principle ally of Riyadh's top regional rival Iran.
On Friday the court set Samaha's new sentence at 13 years, but in Lebanon a prison year is equivalent to nine months.
"The issuance of the verdict on the terrorist Michel Samaha corrects the former lenient verdict, which we had rejected and declared we would not tolerate," said former prime minister Saad al-Hariri, a leading critic of Damascus.
Interior Minister Nohad Machnouk, a member of Hariri's Future Movement, said the new sentence confirmed "the correctness of our trust in the president and members of the court".
Ashraf Rifi, another Sunni Muslim politician, had resigned his post as justice minister over his granting of bail in January after describing the trial last year as a travesty of justice.
Syria is Lebanon's largest neighbor and dominated the country from the end of its civil war in 1990 until 2005, when U.S.-led pressure helped force Syrian troops to leave.
Its ally Hezbollah remains Lebanon's main power broker and has fought alongside government forces in Syria's civil war.
Hezbollah and its leading members made no immediate comment on Friday's sentence.
(Reporting By Laila Bassam and Angus McDowall; editing by John Stonestreet)