WASHINGTON — The US and five Arab countries launched airstrikes Monday night on Islamic State group targets in Syria, expanding a military campaign into a country whose three-year civil war has given the brutal militant group a safe haven.
Using a mix of manned aircraft — fighter jets and bombers — plus Tomahawk cruise missiles, the strikes were part of the expanded military campaign that President Barack Obama authorized nearly two weeks ago in order to disrupt and destroy the Islamic State militants, who have slaughtered thousands of people, beheaded Westerners and captured large swaths of Syria and northern and western Iraq.
Speaking outside the White House on Tuesday, President Barack Obama said the participation of five Arab nations in airstrikes ‘‘makes it clear to the world this is not America’s fight alone.’’
US officials said the airstrikes began around 8:30 p.m. EDT, and were conducted by the US, Bahrain, Qatar, Saudi Arabia, Jordan and the United Arab Emirates. The first wave of strikes finished about 90 minutes later, but the operation was expected to continue for several more hours, according to one US official, who spoke on condition of anonymity because he was not authorized to speak publicly by name about an ongoing mission.
Syria’s Foreign Ministry said the US informed Syria’s envoy to the U.N. that ‘‘strikes will be launched against the terrorist Daesh group in Raqqa.’’ The statement used an Arabic name to refer to the Islamic State group.
At a conference on Sept. 11 with Secretary of State John Kerry, key Arab allies promised they would ‘‘do their share’’ to fight the Islamic State militants. The Obama administration, which at a NATO meeting in Wales earlier this month also got commitments from European allies as well as Canada and Australia, has insisted that the fight against the Islamic State militants could not be the United States’ fight alone.
Because the military operation was ongoing, no details could be provided yet, said Rear Adm. John Kirby, the Pentagon’s press secretary. He said the military made the decision to strike early Monday. A White House official said Obama was being updated.
The strikes were carried out by manned Air Force and Navy aircraft, and the Tomahawk missiles were launched from US ships in the northern Persian Gulf and the Red Sea. The aircraft carrier USS George H.W. Bush is in the Gulf.
Activists said the airstrikes hit targets in and around the Syrian city of Raqqa and the province with the same name. Raqqa is the Islamic State group’s self-declared capital in Syria.
Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, told The Associated Press, ‘‘There is confirmed information that there are casualties among Islamic State group members.’’
He added that missiles also targeted the towns of Tabqa, Ein Issa and Tel Abyad, as well as the village of Kfar Derian, which is a base for the al-Qaida-linked Nusra Front, a rival of the Islamic State group.
Another activist, Mohammed al-Dughaim, based in the northern Syrian province of Idlib, confirmed that several airstrikes hit Kfar Derian in the early hours of Tuesday. He said there were civilians among the casualties.
An amateur video posted online Tuesday shows explosions going off at night in an open area, blasts that are said to be from coalition airstrikes. The narrator in the video is heard saying that the footage shows the ‘‘bombardment of the Kfar Derian village.’’
The head of the main Western-backed Syrian opposition group, Hadi Bahra, welcomed the commencement of airstrikes in Syria.
‘‘Tonight, the international community has joined our fight against ISIS in Syria,’’ he said in a statement, using an alternate acronym for the Islamic State. ‘‘We have called for airstrikes such as those that commenced tonight with a heavy heart and deep concern, as these strikes begin in our own homeland. We insist that utmost care is taken to avoid civilian casualties.’’
Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, told senators last week, ‘‘This won’t look like a shock-and-awe campaign, because that’s simply not how ISIL is organized, but it will be a persistent and sustainable campaign.’’ ISIL is another acronym for the Islamic State group.
Defense Secretary Chuck Hagel said the plan ‘‘includes targeted actions against ISIL safe havens in Syria, including its command and control logistics capabilities and infrastructure.’’ He said he and Dempsey approved the plan.
The US has also been increasing its surveillance flights over Syria, getting better intelligence on potential targets and militant movements. None of Monday’s airstrikes were from drones.
Military leaders have said about two-thirds of the estimated 31,000 Islamic State militants were in Syria.
Some officials have expressed concern that going after Islamic State militants in Syria could inadvertently help Syrian President Bashar Assad, since the militants are fighting in part to overthrow Assad.
In a speech Sept. 10, Obama vowed to go after the Islamic State militants wherever they may be. And his military and defense leaders told Congress last week that airstrikes within Syria are meant to disrupt the group’s momentum and provide time for the US and allies to train and equip moderate Syrian rebels.
The US military has been launching targeted airstrikes in Iraq since August, focusing specifically on attacks to protect US interests and personnel, assist Iraqi refugees and secure critical infrastructure. Last week, as part of the newly expanded campaign, the US began going after militant targets across Iraq, including enemy fighters, outposts, equipment and weapons.
To date US fighter aircraft, bombers and drones have launched about 190 airstrikes within Iraq.
Urged on by the White House and US defense and military officials, Congress passed legislation late last week authorizing the military to arm and train moderate Syrian rebels. Obama signed the bill into law Friday, providing $500 million for the US to train about 5,000 rebels over the next year.
US leaders have also been crisscrossing the globe trying to build a broad international coalition of nations, including Arab countries, to go after the Islamic State group and help train and equip the Iraqi security forces and the Syrian rebels.
The militant group, meanwhile, has threatened retribution. Its spokesman, Abu Mohammed al-Adnani, said in a 42-minute audio statement released Sunday that the fighters were ready to battle the US-led military coalition and called for attacks at home and abroad.
Burns reported from aboard a US military aircraft. Associated Press writers Zeina Karam, Julie Pace and Matthew Lee in New York, Josh Lederman in Washington and Bassem Mroue in Beirut contributed to this report.