Tehran's recent ballistic missile tests did not violate a UN resolution and were not illegal, Foreign Minister Mohammad Javad Zarif said Tuesday after being questioned on the issue by Australia.

The United Nations Security Council met Monday at the request of the United States to discuss the missile tests that have raised the prospect of new sanctions.

But Zarif said that under Resolution 2231, adopted a few days after Iran struck a landmark nuclear deal with world powers last year, Tehran was within its rights to carry out the tests.

He said the wording of the resolution did not use obligatory terms so "Iran is not obliged by 2231".

Secondly, it covered only missiles "designed to be capable of carrying nuclear warheads", he told reporters in Canberra.

"Since we do not have nuclear warheads and we have undertaken not to develop them, and the international community has put in place the best mechanisms money can buy in order to make sure that we do not develop nuclear weapons... we do not design any missiles to carry things we do not have," Zarif said.

"So these missiles do not fall within the purview of 2231 and they are not illegal."

Iran fired two long-range ballistic missiles on March 9, one day after similar tests that came fewer than two months after the Iran nuclear deal was implemented.

Zarif stressed that the missiles were being developed only for Iran's defence.

Under the historic nuclear deal, most UN sanctions resolutions against Tehran were lifted, but an arms embargo and restrictions on ballistic missile technology remain in force.

Australian Foreign Minister Julie Bishop said she had raised the question with her Iranian counterpart, and they had had a "very detailed discussion".

"We discussed the perception, the political circumstances surrounding the timing of this," she said.

"It is Australia's position that should the UN Security Council wish to investigate this matter, then that would be the proper legal process for it to do so."