The U.S. government on Tuesday blacklisted Nusra Front, an al-Qaida-affiliated group it accused of trying to "hijack" the struggles of the Syrian opposition, and hit two of its leaders with sanctions.

The State Department listed Nusra Front as an alias of ai-Qaida in Iraq (AQI), blaming it for nearly 600 terrorist attacks in Syria since November 2011, including more than 40 suicide attacks.

"Through these attacks, Nusra has sought to portray itself as part of the legitimate Syrian opposition while it is, in fact, an attempt by AQI to hijack the struggles of the Syrian people for its own malign purposes," the agency said in a statement.

In some press reports, Nusra Front fighters were described as leading forces in capturing military bases and oil fields in the Syrian opposition's 20-month conflict with the government.

Following the move of the State Department, the Department of Treasury slapped sanctions on Maysar Ali Musa Abdallah al-Juburi and Anas Hasan Khattab, two senior leaders of Nusra Front.

In addition, the Treasury targeted Jaysh al-Sha'bi and Shabiha, two armed militia groups it accused of backing the Syrian government headed by President Bashar al-Assad.

Ayman Jaber and Mohammad Jaber, commanders of Shabiha, were hit with sanctions as well.

"These actions represent continued U.S. government efforts to support the legitimate aspirations of the Syrian people as they seek to free themselves from the oppression of the al-Assad regime and to deny al-Qaida's attempts to subvert the Syrian opposition," the Treasury said in a statement.

"We will target the pro-Assad militias just as we will the terrorists who falsely cloak themselves in the flag of the legitimate opposition," David Cohen, under secretary of Treasury for terrorism and financial intelligence, was quoted as saying.