Turkmenistan has jailed three top central bank officials for 15 years in a graft scandal linked to a construction boom in the capital led by Turkish companies, sources and a report said Friday. A court has sentenced the head of the international transaction department, the head of bank payments department, and its leading expert to 15 years in prison, a maximum term for economic crimes in the isolated Central Asian nation, a state-run newspaper said. Seven more officials have been detained pending an investigation, the newspaper Neutralny Turkmenistan said. A local businessman was also jailed for 15 years. \"The former officials conducted bank fraud and machinations under the pretext of helping to provide credit for various grandiose construction projects which have become symbols of our country,\" the newspaper said. This appeared to be a reference to ambitious projects led by Turkish companies to transform the sleepy provincial ex-Soviet town of Ashgabat into a capital city of marble-clad government offices. \"Under the pretext of expediting bank operations the convicted officials were receiving bribes,\" Neutralny Turkmenistan said. The newspaper said the group received bribes of around $5 million. The public exposure of the officials -- a rare event in one of the world\'s most secretive states -- comes amid reports Turkish companies are preparing to lodge claims against Turkmenistan over $1 billion of unpaid bills. In May, Turkish President Abdullah Gul travelled to Ashgabat for talks with President Gurbanguly Berdymukhamedov in an apparent bid to try and recover the debt. The bank officials may have demanded bribes from the Turkish companies, a source in the government of Turkmenistan told AFP on condition of anonymity. Berdymukhamedov said in June some 600 Turkish companies had undertaken projects in Turkmenistan worth $24 billion, adding that Turkmenistan had supported Turkey at the time of the global economic crisis. The president is seeking to very cautiously ease the country out of its extreme isolation under his eccentric predecessor Saparmurat Niyazov who died in 2006, although critics say stabs at reform have been little more than window-dressing.