US President Barack Obama admitted Thursday that he still does not have a strategy to fight Islamic State jihadists in Syria, as the militants boasted they had executed scores of Syrian troops — the latest in a string of atrocities that have shocked the world.

Dampening hopes of imminent airstrikes in Syria, Obama said he was still developing a comprehensive plan to defeat IS, which has also overrun large swathes of Iraq.

The civil war in Syria has killed some 191,000 people since it erupted in March 2011 with President Bashar Assad’s bloody effort to put down an uprising.

But it has taken on another dimension as IS jihadists exploited the power vacuum to move in, unleashing a series of atrocities including the brutal execution of US journalist James Foley.

The chaotic situation on the ground was underlined by the seizing of 43 UN peacekeepers on the Golan Heights by rival Islamist rebels, led by al-Qaeda affiliate the al-Nusra Front.

A Fighter of the Islamic State group waving their flag from inside a captured government fighter jet following the battle for the Tabqa air base, in Raqqa, Syria on Sunday. (photo credit: AP/Raqqa Media Center of the Islamic State group)

A fighter of the Islamic State group waving their flag from inside a captured government fighter jet following the battle for the Tabqa air base, in Raqqa, Syria, on Sunday. (photo credit: AP/Raqqa Media Center of the Islamic State group)

They were part of a mission that has monitored an armistice between Syrian and Israeli troops on the strategic plateau for decades.

“We don’t have a strategy yet,” Obama said ahead of a meeting with security chiefs.

US Secretary of State John Kerry at a press conference in Cairo with United Nations Chief Ban Ki-moon, on July 25, 2014 (Photo credit: AFP/Pool)

US Secretary of State John Kerry at a press conference in Cairo with United Nations chief Ban Ki-moon, on July 25, 2014 (photo credit: AFP/Pool)

But he said he was dispatching Secretary of State John Kerry to the Middle East to build support in the region against the IS jihadists.

The jihadists posted grisly video footage on the Internet of scores of bodies heaped in the desert they boasted were those of Syrian soldiers they had captured and killed following the seizure of Tabqa air base.

They have repeatedly posted gruesome videos, which have appalled international opinion but served as a propaganda tool to recruit volunteers.

The Britain-based monitoring group the Syrian Observatory for Human Rights said IS had executed at least 160 soldiers, among some 500 who had made a desperate bid to escape to government-held territory after their defeat last Sunday.

‘No need to choose between IS and Assad’

The footage posted by IS showed a close-up of some 20 bodies, but then panned out to show scores more.

Other shots showed men barefoot and dressed only in their underwear walking in line with their hands on their head in surrender, escorted by jihadist gunmen.

One held up the black flag of the jihadists. Others chanted: “Islamic State forever.”

Tabqa was the last position in Raqa province to fall to the jihadists, who now control a vast swathe of northeastern Syria and Iraq.

A UN-mandated probe has charged that public executions, amputations, lashings and mock crucifixions have become a regular fixture in jihadist-controlled areas of Syria.

This undated photo combo taken from a video by the Islamic State group, a Syrian opposition group, which has been verified and is consistent with other AP reporting, shows still images of government soldiers captured near Tabqa, Syria according to a statement posted online and circulated on Twitter by supporters of Islamic State group. The photo to the left shows what the extremist group said were the soldiers stripped down to their underwear marching in the desert. The photo to the right shows more than 150 men apparently killed. (photo credit: AP Photo/ The Islamic State group)

This undated photo combo taken from a video by the Islamic State group, a Syrian opposition group, which has been verified and is consistent with other AP reporting, shows still images of government soldiers captured near Tabqa, Syria, according to a statement posted online and circulated on Twitter by supporters of the Islamic State group. The photo to the left shows what the extremist group said were the soldiers stripped down to their underwear marching in the desert. The photo to the right shows more than 150 men apparently killed. (photo credit: AP/The Islamic State group)

The Syrian government launched airstrikes of its own on Thursday, killing six IS leaders, the Observatory said, but Washington has balked at cooperating with Damascus against the group.

On Thursday, Obama reiterated the stance, saying: “I don’t think there’s a situation where we have to choose between Assad or the kinds of people who carry on the incredible violence that we’ve been seeing there.”

UN peacekeepers held

Rival jihadists of al-Nusra Front, backed by other rebels, detained 43 Fijian peacekeepers on the Golan on Thursday, a day after their capture of the sole crossing over the UN-patrolled armistice line to the Israeli-occupied sector of the plateau.

“Forty-three peacekeepers from the United Nations Disengagement Observer Force were detained early this morning by an armed group in the vicinity of Quneitra,” a UN statement said.

The 43 peacekeepers from Fiji were forced to surrender their weapons and taken hostage, but 81 Filipino blue helmets “held their ground” and refused to disarm, the Philippine defense department said.

It said the Filipino peacekeepers were being surrounded by the gunmen in a stand-off.

The UN Security Council and the US separately condemned the action and demanded the “unconditional and immediate release” of the peacekeepers, a statement said.

Peacekeepers were detained twice last year before being released safely.

The Philippines has said it will repatriate its 331-strong contingent, for security reasons, mirroring previous moves by Australia, Croatia and Japan.

Washington has been weighing both aid drops and airstrikes in Iraq to help residents of a Shiite Turkmen town besieged by the jihadists since early June, US officials said on Wednesday.

“It could be a humanitarian operation. It could be a military operation. It could be both,” said a US defense official on condition of anonymity.

UN Iraq envoy Nickolay Mladenov has called for an urgent effort to help Amerli, saying residents face a “possible massacre” if the town is overrun.