TRIPOLI, Lebanon (CNN) - Two powerful explosions ripped through neighborhoods near mosques in the northern Lebanon city of Tripoli on Friday.
At least 29 people died and more than 500 were wounded in the bomb blasts, Lebanese Red Cross head George Kettanah said, according to Lebanon's state-run National News Agency.
There was heavy gunfire after the explosions, Tripoli residents told CNN.
While the motive for the attacks was unclear, NNA said they appeared to target mosques run by imams with ties to Syrian rebels.
Lebanon has been the scene of increasing sectarian violence recently, including battles between supporters and opponents of the regime in Lebanon's neighbor to the east, which is currently torn by a bloody civil war.
The Lebanese army said it had established a security cordon around the blast sites. The bombs caused "great material damage" in addition to the casualties, the army said.
The first blast occurred near the Sunni al Taqwa mosque, NNA said.
The second occurred minutes later near al Salam mosque, another Sunni mosque that is close to the residence of acting Prime Minister Najib Mikati, as well as Samir Al-Jisr, a Sunni member of parliament and the former head of the country's Internal Security Forces, Ashraf Rifi.
Rifi is despised by Hezbollah and Lebanese politicians friendly to Syrian President Bashar al-Assad.
It was unclear if any of those figures were targets of the attack, but NNA said the mosques' two Salafist sheikhs were unharmed.
Mikati is not in Tripoli, NNA reported.
The second blast produced a crater 5 meters (16.4 feet) across and damaged six nearby residential buildings, NNA said. More than 60 cars were incinerated, the news agency said.
Eyewitness video posted to YouTube purporting to be of the al Taqwa blast showed thick smoke, flames and what appeared to be burning vehicles. Another video posted to Facebook showed a large plume of smoke rising into the air near what is said to be the mosque site.
CNN could not immediately confirm the authenticity of the videos.
Mikati issued a statement via Twitter condemning the bombings.
"We urge our children and brothers in Tripoli to practice self-restraint and we pledge to them that we will always stand by them especially during these critical times," he said.
"Tripoli and its residents he will prove once again that they are stronger than the conspiracy and will not allow the strife to undermine their resilience and their faith in God and the homeland," the acting prime minister tweeted.
Tammam Salam, the man designated to become Lebanon's next prime minister, cut short a private trip to Greece after the explosions.
"The crime of Tripoli is further evidence that the situation in Lebanon reached a very critical stage and requires us to be on high alert on the political, national and security levels in order to eradicate the internal strife, and we have to deal with the political decisions in the country with the highest degree of national responsibility," he said in a prepared statement.
The U.S. Embassy in Beirut also condemned the violence and called on Twitter for "calm & restraint."
Hezbollah also condemned the attacks, saying in a statement that the explosions were part of a "criminal scheme aimed at sowing seeds of strife among the Lebanese."
Hezbollah, the Lebanese Shiite group, is active in southern Lebanon and has been sending its fighters to Syria to help the government there.
A car bombing in a southern suburb of Beirut this month rocked a Hezbollah stronghold, killing at least 22 people and injuring hundreds.