The United States has slapped fresh economic sanctions on Iran, designating 18 individuals and entities for supporting what it said were "illicit Iranian actors or transnational criminal activity".

Heather Nauert, the state department spokeswoman, accused Iran on Tuesday of testing and developing ballistic missiles "in direct defiance" of a UN Security Council resolution.

The US is "deeply" concerned about "Iran's malign activities across the Middle East which undermine regional stability, security, and prosperity," including support for armed groups, the Syrian regime and Houthi rebels in Yemen, she said.

Iran's parliament retaliated by voting for extra funding for the missile programme and its foreign ministry said it would impose its own sanctions against Americans.

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The US treasury department said those sanctioned had backed Iran's military or Iran’s Islamic Revolutionary Guard Corps (IRGC) by developing drones and military equipment, producing and maintaining boats, and procuring electronic components.

Others have also "orchestrated the theft of US and Western software programmes" sold to Iran's government, it said in a statement.

The US state department had also designated two other Iranian organisations involved in Iran's ballistic missile programme, according to the treasury department.

Nuclear deal

The news comes just a day after the US administration declared that Iran was complying with a landmark nuclear deal signed two years ago.

That deal does not cover Tehran's ballistic missile programme.

The US government threatened additional sanctions on Tuesday, saying that although Iran was meeting its requirements on paper, it was "unquestionably in default of the spirit of the accord".

Al Jazeera's Patty Culhane, reporting from Washington, DC, said those listed in the sanctions were now prohibited from using the American banking system, and any assets they have in the US would be frozen.

"These are fairly minor if you compare them to the sanctions lifted as part of the nuclear deal," she said.

Iran's foreign ministry called the fresh sanctions a "worthless act" and "illegal", according to the official news agency IRNA.

READ MORE: US certifies Iran nuclear deal, but vows new sanctions

Tehran "will,in turn, apply new sanctions against American people and entities that have acted against the Iranian people and other Muslim peoples of the region," it reported.

Iran's parliament, in addition to earmarking an additional US$260m for its ballistic missile programme, also agreed to allot a similar amount to the military's foreign operations wing, the Quds Force, which Washington has accused of fomenting unrest across the region.

Ali Larijani, the speaker of Iran's parliament, said the measures would show the Americans that Iran "will resist them with all its power".

While the US complained about Iran's defiance of the spirit of the nuclear accord, Iranian Foreign Minister Mohammad Javad Zarif said he would make his own complaints about US non-compliance when representatives of the five nuclear powers - China, Russia, France, Britain, the US - plus Germany meet in Vienna on Friday to take stock of the deal.

Zarif accused the Trump administration of failing to lift sanctions in line with the deal.