Corruption, a recurring scourge for Algeria, has risen to the forefront of public life during President Abdelaziz Bouteflika's rule, fuelled by soaring oil prices and an the explosion in imports. The judiciary has opened a graft probe centred on state-run energy giant Sonatrach, which has amassed nearly $700 billion in earnings since Bouteflika took office, with political leaders among those named in the investigation. "Oil prices have soared during Bouteflika's 15 years in power. Oil wealth is the cause of the spreading corruption," said Djilali Hadjadj, head of the Algerian Association to Combat Corruption, an NGO. "Those close to the presidential circle and the (political) system are generally involved at different levels," Hadjadj told AFP, estimating that tens of billions of dollars have been pocketed at different levels. But Abdelmalek Sellal, who resigned as prime minister to head Bouteflika's re-election campaign on April 17, retorts that "you can't accuse us of failing to fight corruption". Two thousand cases were investigated in 2012 alone, according to Sellal. Since 2009, a string of graft cases have come to light, most notably one involving former energy minister Chakib Khelil. A Bouteflika protege, Khelil ran the ministry for a decade until 2010, when a corruption scandal at Sonatrach forced him to resign. Between 2000 and 2013, Sonatrach reaped around $670 billion in earnings, which enabled Algeria to finance some $370 billion worth of imports, repay $40 billion in debts and accumulate $200 billion in foreign currency reserves. In August, the Algerian judiciary issued an international arrest warrant for Khelil for a case involving contracts between Sonatrach and foreign companies, including Saipem, a unit of Italian energy major ENI. The move came after prosecutors in Milan, the financial capital of Italy, also opened an investigation into the case. The Algerian arrest warrant for Khelil has since been lifted, on procedural grounds, but the former Bouteflika ally has yet to return to Algeria since leaving for the United States in early 2013. "This is very worrying. At a time when major international corruption scandals have registered progress abroad, it's the status quo in Algeria," said Hadjadj. In a separate case, senior officials from the public works ministry were jailed in 2009 after being implicated in a bribery scandal involving the construction of a major East-West highway. - Competing clans - The cost of connecting Algeria's borders with Tunisia and Morocco -- a distance of 1,227 kilometres (762 miles) -- was initially estimated at $7 billion, but is now expected to reach $13 billion, said economist Abderahmane Mebtoul. Some 16 percent of this amount has been distributed in bribes, according to El Watan newspaper. The revelation of these recurring scandals has been variously interpreted, with some saying they indicate that the authorities are actually fighting corruption, and others arguing that they reflect a power struggle among the ruling clans. Intelligence services, which until last year had a monopoly on graft probes, are "playing their cards via the press to neutralise or eliminate any troublesome opponents at the summit of power," said analyst Mohamed Hachemaoui. Amar Saidani, the secretary general of the ruling National Liberation Front (FLN) who the press have implicated in one such case, said the DRS intelligence agency "never ceases to invent stories about circles close to the president". Although most corruption cases have emerged during Bouteflika's third term, a major scandal rocked Algeria in 2002, three year after he came to power, when the business empire of Rafik Khalifa, the son of a former intelligence chief, collapsed. The bankruptcy of the Khalifa group, which included a bank, an airline and television stations, cost the Algerian state and individual investors between $1.5 and $5 billion. Khalifa, who controlled the group and had been considered Algeria's golden boy as the country emerged from a decade of bloody civil war, fled to Britain in 2003 and was sentenced in absentia to life imprisonment. Finally extradited to Algeria in December, he is now in custody awaiting a new trial. Algeria was ranked 94th out of 177 countries and territories in Transparency International's Corruption Perceptions Index for 2013. A number one ranking means the least corrupt.