Harakat al-Nujaba and Hezbollah have fought side-by-side to bolster Syrian government troops since 2013, most prominently against the Islamic State group in eastern Syria.

On Tuesday, the movement's secretary general Akram al-Kaabi visited the tomb of top Hezbollah commander Imad Mughniyeh to commemorate the 10 years since his death.

"We in the Iraqi resistance stand with Hezbollah, and we will stand with Hezbollah in any Israeli attack or action against it," Kaabi said.

He pledged to fight "with Hezbollah in a single row, on a single front, just as we stood with them on a single front in Iraq or Syria."

Kaabi spoke in Beirut's southern suburbs, where Hezbollah has a strong support base.

Both Harakat al-Nujaba and Hezbollah are backed by Iran. They fought alongside Syrian government troops and other allied militia to oust IS from key cities in eastern Syria last year, including Albu Kamal.

Hezbollah has also dispatched top commanders and advisers to Iraq to help the paramilitary Hashed al-Shaabi force.

In June, Hezbollah chief Hassan Nasrallah warned that hundreds of thousands of Arab and Muslim fighters would be ready to fight against Israel if it waged a new attack.

It "would open the door for hundreds of thousands of fighters from all around the Arab and Islamic world to participate in this fight -- from Iraq, Yemen, Iran, Afghanistan, Pakistan," he said.

Kaabi is the second top Iraqi militia leader in recent months to come to Lebanon in a show of support to Hezbollah.

Senior Hashed commander Qais al-Khazali, who heads the Asaib Ahl al-Haq militia, visited southern Lebanon in December.