The United States unveiled sanctions Monday on former Afghan parliament speaker Mir Rahman Rahmani and his son Ajmal Rahmani, alleging they misappropriated millions of dollars from US government-funded contracts.

"Through their Afghan companies, the Rahmanis perpetrated a complex procurement corruption scheme," the Treasury Department said in a statement.

It added that the millions in misused funds were from contracts that supported Afghan security forces.

Besides designating the Rahmanis, Treasury also took aim at 44 associated companies.

The sanctions fall under the Global Magnitsky Human Rights Accountability Act, and freeze assets those blacklisted have under US jurisdiction, forbidding Americans and US companies from doing business with them.

The US State Department has also designated the Rahmanis and their immediate family members for "involvement in significant corruption as a public official."

Among the Rahmani's alleged wrongdoings were artificially inflating the price of fuel contracts they won, and using their hidden control of companies to boost fuel contract prices by fraudulently submitting bids, the Treasury said.

Their companies' representatives were also said to have bribed Afghan Customs officials for more documents that allowed them to import goods tax free. The Rahmanis are also accused of under-delivering contracted fuel, the statement said.

The 44 companies designated include 21 German firms and eight in Cyprus.