The source said the sailors are being held on charges of carrying fire arms and illegal navigation in the Iranian waters on the order of a local court.
According to the source, the tanker was shipping 6,000 tons of gas oil in Arvand river bordering Iraq, when it was seized by Iranian border guards and its crew were arrested last month.
In June, Iranian naval guards seized three British vessels in the country's territorial waters in Arvand river and detained eight sailors.
The servicemen, two Royal Navy sailors and six Royal Marine commandos, were later released.
Their equipment reportedly consisted of personal weapons, radios and navigation equipment, including echo sounders to measure the depth of the water, global positioning systems to identify the exact position and up-to-date maritime charts.
The Times newspaper has said that Iran had agreed only 'in principle' to return the boats, but that there had been little progress about the manner in which they would be given back.
Iran has been wary of the occupation forces' presence on its doorsteps in Iraq and carefully watched their movements.
Tehran, while opposing Iraq's invasion, took a position of 'active neutrality' at the time of the attack.
... Payvand News - 12/13/04 ... --