Amid escalating tensions between the U.S. and Iran, eight people including Iraqi militiamen, Iraqi officials, and Syrian activists were killed in an attack by unidentified planes that hit targets in Syria Friday. According to the Iraqi officials, the death toll could rise further since some militiamen were in serious condition.

The warplanes targeted the areas that belonged to pro-Iran militias in the Boukamal area, near the border with Iraq, according to the Syrian Observatory for Human Rights. The planes also struck militias' vehicles and weapons depots, the organization added.

An Iraqi security official and another official from the Iran-backed Iraqi militias- Popular Mobilization Forces (PMF) believe that it was the Israeli warplanes that carried the strike. The planes, they said, targeted two vehicles that were carrying missiles on the Syrian side of the border. However, they had no evidence to back their statements.

Israel has, in the past, also struck Iran-linked targets in Syria and warned against any permanent Iranian presence there, Associated Press reported.

The Syrian Observatory for Human Rights which is a Britain-based organization has many activists who file the Syrian war. As per one of the activists, the planes struck the trucks carrying weapons and depots for ballistic missiles in the area. Another told the attack triggered “a huge explosion” that could be heard in the Syrian-Iraqi border.

On Dec. 29, the U.S carried out military strikes against a pro-Iran militant group in Iraq, killing 19 fighters, two days after a rocket attack on a military base in Iraq that killed an American civilian contractor.

The top commander of Iran's Revolutionary Guards-Quds Force, Gen. Qasem Soleimani, was assassinated in an airstrike on Jan.2, just outside of the Baghdad airport on President Donald Trump's order. This came after the U.S. embassy in the Iraqi capital was seized by the members of Iranian-backed Shiite militias- the PMF.

In response to the killing of Qasem, Iran fired a volley of missiles at U.S. bases in Iraq that host U.S. troops. However, no U.S. casualties were reported from the attacks.

The area that was struck Friday is the key to a land corridor for Tehran, linking Iran across Iraq and Syria through Lebanon.