Two explosions targeted mosques packed with worshipers in the northern Lebanese city of Tripoli Friday, killing at least 27 people.

The bombs detonated outside two Sunni mosques in the port city, located 50 miles north of Beirut, as worshipers gathered for Friday prayers.

Lebanese television stations showed huge plumes of smoke rising from the explosion sites Friday, as bleeding victims and dead bodies were carried away from the wreckage.

The bombings came eight days after an explosion killed 27 people in a Shiite suburb of Beirut that was a stronghold of the Iranian-supported Hezbollah.

The Aug. 15 explosion was the country’s most deadly bombing since the 1980s, and analysts warned it could mark a new era of Sunni vs. Shiite retaliatory bombings targeting civilians, The Washington Post reported.

No one had claimed responsibility for the Tripoli bombings by Friday afternoon. Lebanon’s caretaker prime minister Najib Mikati blamed the “hand of criminality” for the bombings, which he described as “a clear message aimed to plant strife.”

One of the explosions targeted al-Taqwa mosque, where the Salafi cleric Salem al-Rifai preaches. Rifai survived an assassination attempt in April, when gunmen opened fire outside the mosque’s entrance.

Another bomb hit Tripoli’s al-Salam mosque. At both mosques, the imams escaped safely, according to Lebanon’s state-run National News Agency, which said as many as 352 people were injured in the two blasts. Hospitals put out calls for donations of blood.

Tripoli, a poverty-stricken coastal city, has a reputation for being Lebanon’s most volatile and the one where the country’s deeply rooted sectarian fault lines are most pronounced.

Sunni gunmen regularly battle Tripoli’s small community of Alawites, who are an offshoot of the Shiite sect and co-religionists of Syrian President Bashar al-Assad.

Since the outbreak of civil war in Syria more than two years ago, Sunni- Alawite clashes have grown more frequent, especially since Lebanon’s Shiite Hezbollah group sent troops to Syria to help Assad battle the Sunni-dominated rebels.

Earlier Friday, Israel said it bombed a militant group’s base in Lebanon in response to the launching of four rockets across its northern border Thursday afternoon. It was Israel’s first airstrike inside Lebanon since its 2006 war with Hezbollah, the Post reported.

The target was reportedly a base belonging to the Popular Front for the Liberation of Palestine-General Command (PFLP-GC), a longtime ally of the Assad regime in Damascus, near the town of Naameh, just 10 miles south of Beirut.

The escalation comes at a time of increased tension between Lebanon and Israel. Hezbollah claimed responsibility last week for planting explosives that injured four Israeli soldiers near the Lebanon border in early August.

In a statement, the Israeli military described the cross-border rocket attack Thursday as “a blatant breach of Israeli sovereignty that jeopardized Israeli civilian life.” An Israeli military spokesman said the pilots who carried out the retaliatory airstrike “reported direct hits on the target,” adding that, “Israel will not tolerate terrorist aggression originating from Lebanese territory.”

On Thursday, the Lebanese branch of the Abdullah Azzam Brigades, an Islamist group with links to al-Qaeda, said it had carried out the rocket attack. The group, known as the Ziad al-Jarrah Battalion, is named after a 9/11 hijacker from Lebanon.