(CNN) -- Four rockets struck strongholds of the militant group Hezbollah in Lebanon on Sunday, highlighting fears of sectarian tensions in the country that seem to mirror the strife in the Syrian civil war.
The first two struck a predominately Shiite Beirut suburb of Dahiye, Lebanon's state news agency reported.
One of the rockets injured five people, including three Syrians, the National News Agency reported. The number of casualties from the second one was not immediately known.
Two more rockets pounded a residential area in the northern city of al-Hermel, also a Shiite neighborhood, causing property damage, NNA reported.
Syrian rebels have shelled al-Hermel in the past, saying they are responding to military support of the Syrian regime by Hezbollah, which is a Shiite militia.
Authorities have not identified any suspects in Sunday's attacks.
Concerns that sectarian strife in Syria may trigger ethnic conflict within Lebanon's borders escalated Saturday, when Hezbollah declared it is going to war in Syria on behalf of Syrian President Bashar al-Assad's regime.
Lebanon's caretaker interior minister reflected the anxiety when he visited the site of Sunday's attack, which he called "an act of sabotage to create tensions."
"God willing, the events in Syria will not spill over into Lebanon, and we hope that we will have more men with more reason because we just went over 40 years of civil war," Marwan Charbel told NNA.
At the same time, he emphasized that he does not know who is to blame for the attack.
Like Syria, Lebanon's population is divided into religious and ethnic factions, some bitterly at odds with each other.
Hezbollah is one of the largest and best armed factions. It draws most of its foreign support from Shiite-dominated Iran and from the al-Assad government in Syria, which the U.S. accuses of acting as a conduit for Tehran's weapons deliveries.
His fighters have participated unofficially in towns close to Lebanon's border alongside Syrian government troops in battles against al-Assad's opponents. On Saturday, Hezbollah Secretary-General Hassan Nasrallah promised al-Assad victory with Hezbollah's help.
Nasrallah also called for his opponents in Lebanon to fight against Hezbollah on Syrian soil, hoping to divert armed conflict away from Lebanon and into the active battle field next door.
"We are fighting in Syria, so let us fight there instead and deflect Lebanon from the conflict, the fighting, the confrontations and the bloodshed," he said.
Charbel acknowledged the dangerous potential in Lebanon's rising tensions.
"We are now living in an intolerable environment."
CNN's Nada Husseini in Beirut contributed to this report.