Iran is increasing its level of support to Syria's forces as they continue their brutal crackdown against opposition strongholds, The Washington Post reported Sunday, citing three unnamed US officials.

Citing intelligence reports from the region, the US officials said there had been a spike in the quantity of arms and other aid supplied to Syria by Iran.

"The aid from Iran is increasing, and is increasingly focused on lethal assistance," one of the officials told the newspaper.

The increased support to Bashar al Assad's government comes as US intelligence shows that an Iranian operative was recently injured while working with Syrian forces inside the country.

"They've supplied equipment, weapons and technical assistance -- even monitoring tools -- to help suppress unrest," a US official told The Post. "Iranian security officials also traveled to Damascus to help deliver this assistance."

The UN estimates more than 7,500 people have been killed in the crackdown on protesters calling for an end to Assad's rule.