Investigators have said that more than $1 billion in Saudi Arabian currency has been sent to Afghanistan in the past four years, likely to support terrorism.

The funds had gone through Pakistan, where they were converted into rupees or dollars, The Times of London quoted members of FinTraca, the Afghan intelligence unit, saying.

Mohammed Mustafa Massoudi, director general of FinTraca in Kabul, said, "We can trace it back as far as an entry point in Waziristan. Why would anyone want to put such money into Waziristan? Only one reason -- terrorism."

The flow of cash from Saudi Arabia to Afghanistan has been on the increase and reached the highest rate this year since FinTraca was established in 2006 with U. S. and British help.

The Times further said that Saudi Arabia is an ally in the war on terror, but a U. S. government report last year found private Saudi supporters were the leading source of financing for the Taliban.

FinTraca also said that most of the cash enters Afghanistan through al-Qaida-dominated territory in the Pakistani tribal area.

Insurgents must renounce al-Qaida ties before they will be allowed to become involved in the political process, Afghan authorities have said. (With Inputs from Agencies)