Iran's parliament has unanimously passed a bill designating the United States' forces as "terrorists" over the assassination of top military commander Qassem Soleimani in an air attack in Iraq last week.

Soleimani, the popular head of the Islamic Revolutionary Guard Corps' (IRGC) foreign operations arm Quds Force, was killed in a US drone attack outside Baghdad airport on Friday, ratcheting up tensions between the arch-foes.

Under the newly adopted bill on Tuesday, the entire US forces and employees of the Pentagon and affiliated organisations, agents and commanders and those who ordered the "martyrdom" of Soleimani were designated as "terrorists".

"Any aid to these forces, including military, intelligence, financial, technical, service or logistical, will be considered as cooperation in a terrorist act," the bill said.

Al Jazeera's Assed Baig, reporting from Tehran, said the bill is an amendment to a previous motion passed in April last year which designated the US Central Command as a "terrorist organisation" and declared the US a "state sponsor of terrorism". 

That blacklisting came after the US designated IRGC a "terrorist organisation".

Baig said legislators also voted for 200-million euros ($224-million) to be allocated to the Quds Force "to boost their defensive power".

Tensions between Iran and the US have escalated dramatically after Soleimani's assassination, with Iranian leaders pledging to retaliate and avenge his death.

On Tuesday, tens of thousands of mourners gathered in the city of Kerman, Soleimani's hometown, for his burial, marking the end of a three-day mourning period.