May 25, 2017 0416 GMT
Moscow also started an oil-for-goods swap with Tehran, showing the Kremlin's determination to boost economic ties with Tehran.
The moves come after world powers, including Russia, agreed to a framework with Iran on its nuclear program and signal Moscow’s interest in having a head-start in the race to benefit from an eventual lifting of sanctions on Tehran, Reuters reported.
The Kremlin said Putin signed a decree lifting Russia's own ban on the delivery of S-300 anti-missile rocket system to Iran, removing a major irritant between the two after Moscow cancelled a corresponding contract in 2010 under pressure from the West.
A senior government official said separately that Russia has started supplying grain, equipment and construction materials to Iran in exchange for crude oil under a barter deal.
Sources told Reuters more than a year ago that a deal worth up to $20 billion was being discussed with Tehran and would involve Russia buying up to 500,000 barrels of Iranian oil a day in exchange for Russian equipment and goods.
Officials from the two countries have issued contradictory statements since then on whether a barter deal has been signed, but Deputy Foreign Minister Sergei Ryabkov indicated one was already being implemented.
"I wanted to draw your attention to the rolling out of the oil-for-goods deal, which is on a very significant scale," Ryabkov told a briefing with members of the upper house of parliament on the talks with Iran.
Iran attends Shanghai confab
Putin’s order came as Shamkhani arrived in Moscow on Monday to attend the 10th meeting of the National Coordinators of Shanghai Cooperation Organization (SCO) and hold meetings with Russian officials.
In a meeting with Secretary of the Security Council of Russian Federation Nikolai Patrushev, Shamkhani hailed cooperation between Iran and Russia as a major factor in managing security crises across the region.
Shamkhani deplored the "destructive role" of certain Western countries and their allies that have violated the globally accepted moral, humanitarian and legal standards, and have set the ground for the destruction of the regional countries' resources.
"The worrisome spread of security crises and institutionalization of violence and extremism have necessitated the active and balancing role of independent countries more than ever," he said.
The SCO meeting opened on Monday with the participation of its member-states, namely Kazakhstan, China, Kyrgyzstan, Russia, Tajikistan and Uzbekistan, and representatives of observer states, namely Afghanistan, India, Iran, Mongolia and Pakistan. It is to focus on regional security and developments.