Iraqi populist Shiite cleric Muqtada Al Sadr condemned the Tehran-backed Shiite militias' support towards victims of flash flooding in Iran.
A convoy of 50 vehicles carrying member of the militias, also known as the Hashed Al Shaabi, arrived in western Iranian provinces that were severely affected by the flash flooding, Iranian news agency Tasnim reported on Sunday.
"Iraqis come first," Mr Al Sadr said on Twitter, adding that there are many areas in Iraq that are at risk of flooding from torrential rain.
"Since there are those who have provided relief to affected areas in Iran, it is our duty to intensify our efforts to provide relief to our people in Iraq," he said.
The Hashed Al Shaabi was formed in 2014 to assist Iraqi forces defeat ISIS but are accused of exploiting its position and human rights breaches.
Mr Al Sadr said relief activities should be kept at a minimum level to the Iraqi army and should be directed towards locally established committees.
He called for assistance from the international community towards Iraq, stressing that the aid “should not be used for political purposes”.
Last week, Iraqi authorities warned of the likelihood of a catastrophic collapse of the country’s largest hydroelectric dam in Mosul due to torrential rainfall.
If the dam fell, it would unleash a wave of water almost 90 metres high, experts said.
Weeks of bad weather have led to floods in Iraq that have displaced hundreds of families and destroyed crops and farmlands.
Iran's ambassador to Iraq, Irj Masjedi, told Iranian news agencies on Saturday that the Hashed Al Shaabi's forces have been deployed to western Iran to help with flood relief.
“Hundreds of Iraqi militia, including 200 on Friday, have arrived in Iran to help the flood-hit people in Kuzestan and Lorestan provinces in western Iran,” Mr Masjedi said.
The Iraqi aid convoy included 26 trucks of engineering equipment, six ambulances as well as 20 trucks of medical and food supplies.
The militias said in a statement that they have transferred their engineering units and heavy machinery to block the flow of floodwater into Iraq.
It comes as the Union of Muslim Scholars in Iraq also appealed for aid for Iranians impacted by the floods.
The union said it has carried out a campaign to collect $75,000, which will be spent on food and medical supplies for more than 1,000 Iranian families.
Earlier this month, Iraqi authorities announced they will close the Al Sheeb border crossing with Iran to trade and travellers until further notice as the flooding continued.
The shutdown comes after a request from Iran, Iraq's Border Ports Commission said.
The water has so far destroyed towns and villages and killed more than 70 people since March 31.
The floods were caused by the worst rain in Iran in a decade and the situation was exacerbated by floodwater rushing down from the north.
Last week, Iranian officials ordered scores of villages to be evacuated as the effects of severe flooding spread further across the country, impacting 20 of its 31 provinces.