Two rockets hit a Hezbollah stronghold in Beirut Sunday morning, wounding four people, in an apparent spillover from the conflict in Syria.

One rocket hit a car dealership in the Mar Mikhael district, injuring four workers. The other hit the second floor of an apartment building in the Chiyah district, where no injuries were reported.

The rockets hit in parts of Beirut controlled by the Shi'a movement Hezbollah, which officially announced Saturday that it was supporting Syrian President Bashar Al-Assad against the rebels. Hezbollah is classified by the United States and Israel as a terrorist organization.

There was no claim of responsibility for Sunday’s attack. But a Syrian rebel commander threatened last  week to strike Hezbollah strongholds in retaliation for the militia’s support for Assad. 

The Syrian conflict has been raging for more than two years, but this is the first time that Beirut’s Shi’a suburbs have been targeted. The rockets were fired less than a day after Hezbollah leader Hassan Nasrallah openly declared that Hezbollah would provide military support to Assad's government.

“We will continue to the end of the road. We accept this responsibility and will accept all sacrifices and expected consequences of this position,” Nasrallah said in the speech Saturday.

Nasrallah said that if Sunni rebels took over in Syria, they would pose an immediate threat to all of Lebanon. Assad's fall would also benefit Hezbollah's archenemy, Israel, he said. Israel has already bombed sites in Syria where it says weapons bound for Hezbollah were located.

Fawaz Gerges, professor of Middle Eastern politics and international relations at the London School of Economics told CNN’s Fareed Zakaria that Iran, as well as Hezbollah “have made it very clear, Assad is a red line.”

No one has claimed responsibility yet for the Beirut attack yet, Lebanese Interior Minister Marwan Charbel said. Charbel said that the rockets were fired from somewhere in the southeast. Security agencies are reportedly looking for a third rocket that was fired but not detonate.

The Lebanese army later discovered two 107mm rocket launchers in a wooded hillside between the villages of Bsaba and Aitit five miles to the south, the Christian Science Monitor reported. A third launcher was discovered nearby but the rocket had misfired.