Two men hug during the funeral for slain 18-year-old Libyan youth activist Tawfiq Bensaud in Benghazi on Saturday. (Abdullah Doma/AFP/Getty Images)

A string of assassinations over a 24-hour period in Benghazi has heightened tensions in the already blood-soaked Libyan city, raising fears that the killings could initiate an even deadlier wave of violence as the country threatens to fracture.

Benghazi residents said Saturday that they were stunned by the speed and scope of the assassinations, in which at least 10 people were gunned down from Thursday to Friday night. Among the dead: a former head of the Libyan air force and a prominent Muslim cleric.

One of those killed was Tawfiq Bensaud, an 18-year-old youth activist. In a photograph circulated on social media, Bensaud, with a toothy grin and a mop of unkempt hair, held a sign that read: “Smile, you are in Benghazi.”

“It’s depressing. The people who were killed came from all walks of life,” said Mustafa Sallak, a Benghazi-based doctor. “Soldiers, activists, sheiks,” he said. “People are afraid.”

No group has claimed responsibility for the killings, and locals and activists said it was unclear whether the assassinations were part of a coordinated assault on high-profile figures or were simply a series of tit-for-tat killings in a city plagued by lawlessness.

Benghazi, nestled on the Mediterranean coast in Libya’s restive east, has suffered from a security vacuum that has allowed militias to run amok. Once the hopeful heart of the 2011 rebellion against Libyan leader Moammar Gaddafi, Benghazi quickly became a bellwether of the country’s descent into chaos. That violence has included the Sept. 11, 2012, attack on a U.S. diplomatic mission in which U.S. Ambassador J. Christopher Stevens and three other Americans were killed.

The country has failed to forge credible institutions in the wake of the revolution, leaving a jumble of armed groups vying for influence in the desert nation’s urban centers.

In May, a rogue former general, Khalifa Hifter, launched a military campaign to stamp out Benghazi militias that the city’s residents blame for the rise in bombings and assassinations over the past several years. But Hifter’s offensive, which prompted the removal of the Islamist-dominated Libyan parliament through fresh elections, only exacerbated the turmoil.

Two months later, armed fighters opposed to Hifter’s operation attacked the international airport in the Libyan capital, Tripoli, ousting another brigade, Zintan, nominally aligned with Hifter. The subsequent fighting between the two sides left scores dead and displaced tens of thousands, according to the United Nations. In a report released this month, the United Nations said attacks by armed groups in Tripoli and Benghazi were “indiscriminate” and having a dire impact on civilian infrastructure in the two cities.

“There is a struggle for power in Libya, and this is the result,” said Hafez al-Aqouri, a former spokesman for Libyan Shield, a Benghazi-based umbrella organization for a cluster of militias.

Aqouri said that his cousin was assassinated Thursday and that the family did not know who was responsible for his murder.

“It could be retaliation for other killings, or it could be tribal,” he said, adding that his family belongs to one of the largest tribes in Benghazi. “Or it could be part of the ongoing struggle between [Hifter] supporters and the revolutionaries,” he said. Many Islamists refer to the Benghazi militias as “revolutionaries” for their role in battling Gaddafi forces during the uprising.

In the case of the slain prominent cleric, Sheik Nabil al-Sati, the motives for his death were also murky. Some residents reached by telephone Saturday said he was an outspoken critic of Hifter, suggesting that forces loyal to the general had killed him. But others said he might have been slain by extremists, such as members of the jihadist group Ansar al-Sharia, who were targeting moderate religious leaders in the city.

“There are many sides carrying out assassinations, and Ansar al-Sharia is just one of them,” said a former fighter with Rafallah Sahati, an ultraconservative ­Islamist militia in Benghazi, who spoke on the condition of anonymity for fear of reprisal. He said his life has been threatened by jihadists as well as former members of Gaddafi’s regime and Libyan separatists.

“This violence is a tremendous waste,” Aqouri said. “These killings will only spark more killings.”

Heba Habib contributed to this report.