Russia is receiving munitions and military hardware sourced from Iraq for its war effort in Ukraine with the help of Iranian weapons smuggling networks, according to members of Iranian-backed Iraqi militias and regional intelligence services with knowledge of the process.

RPGs and anti-tank missiles, as well as Brazilian-designed rocket launcher systems, have been dispatched to Russia from Iraq as Moscow’s campaign has faltered in the last month, the Guardian has learned.

An Iranian-made Bavar 373 missile system, similar to the Russian S-300, has also been donated to Moscow by the authorities in Tehran, who also returned an S-300, according to a source who helped organise the transport.

Using the weapons-trafficking underworld would signal a dramatic shift in Russian strategy, as Moscow is forced to lean on Iran, its military ally in Syria, following new sanctions triggered by the invasion of Ukraine.

The developments also have huge implications for the direction and volume of trade in the international weapons trafficking business.

Iraq has hosted US and western troops since the 2003 overthrow of Saddam Hussein, and the US has trained and supplied various Iraqi army and special forces units to defend the Baghdad government against insurgencies. After two decades of war, the country is awash with weaponry.

Much of it has passed legally into the hands of Iran-backed Shia militias, which are opposed to the US presence in the country, but since 2016 have been officially incorporated into the Iraqi armed forces as part of the fight against Islamic State.

Known for their efficiency in dismantling Islamic State’s “caliphate” – and for their brutal treatment of Sunni civilians – these groups have become powerful actors in Iraq’s security establishment.

RPGs (rocket-propelled grenades) and anti-tank missiles in the possession of Hashd al-Shaabi, the most powerful Shia militia umbrella, were transported to Iran through the Salamja border crossing on 26 March, where they were received by the Iranian military and taken on to Russia by sea, said a commander of the militia branch that controls the crossing.

Ḥashd al-Shaabi also dismantled and sent in pieces two Brazilian-designed Astros II rocket launcher systems, known in Iraq as the licence-built version Sajil-60, to Iran on 1 April, according to a source within the organisation.

“We don’t care where the heavy weapons go [because we don’t need them at the moment],” one Hashd al-Shaabi source said. “Whatever is anti-US makes us happy.”

Three cargo ships capable of carrying such loads – two Russian flagged and one Iranian flagged – crossed the Caspian Sea from Iran’s port of Bandar Anzali to Astrakhan, a Russian city on the Volga delta, within the timeframes outlined.

“What the Russians need in Ukraine right now is missiles. These require skill to transport as they’re fragile and explosive, but if you are committed to doing it, it’s possible,” said Yörük Işık, an Istanbul-based maritime affairs expert. “It’s also not the kind of activity that would be picked up by satellite imagery as they can be transported in large boxes and regular shipping containers.”

Mohaned Hage Ali, a fellow at the Carnegie Middle East Center, said: “That kind of sophisticated weaponry [rocket launcher systems] would make a big difference on the ground in Ukraine. Ḥashd al-Shaabi controls much of the border region with Iran, which would make this transaction easier.

“Other countries such as China are having to be very careful about giving weapons to Russia now, given the new sanctions situation. And Iran, as part of that axis, wants to make sure Russia doesn’t lose ground in this conflict.

“If the Putin regime is destabilised that has huge implications for Iran, particularly in Syria, where Damascus is dependent on Russian air support and Russia coordinates to avoid direct conflict between them and Israel.”

Extensive economic sanctions imposed on Moscow by western nations since the 24 February invasion have included bans on dual-use goods – items with a civilian and a military purpose – such as spare parts for vehicles and certain types of electronics and optical devices, as well as items with obvious military uses.

Russian manufacturers have reportedly been hit hard by the new restrictions, with Ukraine saying that the country’s main armoured vehicle plant, as well as a tractor factory, have run out of parts for making and repairing tanks.

Revised western estimates are that 29 of Russia’s original battalion tactical groups are now “combat non-ineffective” from an invading force that is estimated at 125 battalions, or about 75% of Russia’s total army, in the six-week-old “special military operation”.

The significant losses have yielded few gains: Moscow for now appears to have abandoned its initial attempt to seize the capital, Kyiv, instead drawing down and repositioning its ground forces for a renewed assault on the Donbas region, in the south-east of the country.

Airstrikes and artillery assaults are expected to continue on the cities of Kharkiv and Mykolaiv as well as the besieged port of Mariupol.

Last week, the Ukrainian intelligence services accused Georgia of helping Russia receive sanctioned military materiel, in another potential sign of the scale of the Kremlin’s new efforts to use international smuggling networks to aid its campaign in Ukraine.

Georgian special services received instructions from the country’s political leadership not to interfere with smuggling channels from “east Asia” designed to circumvent new western sanctions, Kyiv’s intelligence directorate said in a statement.

Georgian officials said the Ukrainian claims were baseless. Relations between the two post-Soviet nations have sharply deteriorated since the conflict broke out over the pro-Russian government in Tbilisi’s refusal to impose economic sanctions on Moscow.

US officials have also said that Russia has asked China for military-grade weapons and aid in support of its Ukraine operation.

Russian ally Serbia took the delivery of a Chinese anti-aircraft system in a secretive operation over the weekend, the Associated Press reported, amid western concerns of an arms buildup in the Balkans at the same time as the war in Ukraine which could threaten the fragile peace in the region.

The Guardian