A military prosecutor has accused Adel Qudah, a former finance minister, Mohammed Rawashdeh, a senior economic adviser to the prime minister, and Ahmad Rifai, former head of the country's sole refiner, of receiving bribes and exploiting a public position for personal gain.
Khaled Shaheen, ranked as one of the country's wealthiest businessmen, was accused of "offering bribes and encouraging public officials to abuse their posts."
Qudah, a member of Jordan's political old guard, is the first senior government official to answer corruption charges.
Prime Minister Samir Rifai pledged to fight corruption when he assumed office last December. Critics accused his predecessor of failing to crack down hard enough on corruption, which they blamed for scaring away investors.
Rifai's appointment by the monarch heralded a wider shakeup to ward off popular discontent over economic contraction after years of growth and allegations of rampant official corruption.
Until the latest arrests, moves to tackle graft in the administration and state-controlled companies had been limited to minor investigations and arrests.
Prosecutors say Qudah gained personally during his tenure as the government-appointed chairman of Jordan Petroleum Refinery when he allegedly sought to give a front company Shaheen owned an exclusivity deal to undertake a billion dollar project to expand the country's sole refinery.
No money was involved in the deal that never went through after investors withdrew last year after the global downturn.
The media were barred at the trial's first session in which the four defendants denied the charges read to them by military prosecutors, judicial sources told Reuters. Lawyers contested the court's legality and said it violated the principle of separation of powers as it was not independent from government.
"This is an unjust trial, which is character assassination and a settling of scores among top business interests," said Ahmad Najdawi, a lawyer defending Qudah. Shaheen had been for over a decade the government's contractor of choice for big security projects.
Companies associated with Luxembourg-registered Shaheen Business and Investment Group (SBIG) undertook the construction of a US-funded police academy that has trained Iraqi and Palestinian police.
Shaheen's family concern was also in partnership with government agencies to sell Iraqi oil in the months preceding the fall of former Iraqi President Saddam Hussein in 2003.
