US President Barack Obama has vowed to continue the fight against Islamic State militants after the first American-led air-strikes targeting the group in Syria.
America has announced that dozens of militants were killed yesterday when its jets dropped 160 munitions on Islamic State positions in Syria.
Speaking at the White House, Mr Obama has pledged to build even more international support for the effort, and said more than 40 countries had offered to help. He said America would not tolerate safe havens for terrorists.
US and Arab strikes on militant targets in Syria overnight were just a start of a coalition effort to weaken Islamic State, an extremist group that has killed thousands and beheaded at least three westerners while seizing control of parts of Syria and north-western Iraq, Reuters reports.
"I can tell you that last night's strikes were only the beginning," Rear Admiral John Kirby, the Pentagon press secretary, told reporters. He said the strikes had been 'very successful' and would continue.
Another military spokesman said Arab nations, including Saudi Arabia, Jordan, Bahrain and the United Arab Emirates, took part in the second and third waves of attacks.
President Obama said the US was "proud to stand shoulder to shoulder with these nations".
The Pentagon said warplanes, drones and Tomahawk cruise missiles were used in the strikes.
Mr Obama said he would meet with Iraqi Prime Minister Haider al-Abadi and "friends and allies" at the United Nations to continue building support for the coalition against the Islamic State group.
Islamic State has seized large areas of Syria and Iraq, and the US has launched nearly 200 air strikes in Iraq since August, according to the BBC.
But Monday's strikes mark the expansion of the anti-IS campaign across the border into Syria for the first time.
The strikes targeted the group's main headquarters in its stronghold of Raqqa, north-eastern Syria.
IS training compounds, vehicles and storage sites were also hit in several other areas.
The attacks were organised in three separate waves, Pentagon spokesman Lieutenant General Bill Mayville told reporters.
US fighter jets carried out the first set, with the Arab nations participating in the second and third waves, he added.
President Obama said al-Qaeda-linked militants, known as the Khorasan Group, were also targeted by eight air strikes in Syria.
"We will not tolerate safe havens for terrorists who threaten our people," he said.
President Obama warned that the operation against IS would take some time, but that he would do "what is necessary" to defeat the extremists.
United Nations response
UN Secretary General Ban Ki-moon said that extremist groups operating in Syria "pose an immediate threat to international peace and security," but stopped short of endorsing the air strikes.
"I also note that the strikes took place in areas no longer under the effective control of that government," he told reporters at the UN headquarters in New York.
The UN refugee agency said it was preparing for the arrival of several hundred-thousand Syrian refugees in Turkey, as IS militants advanced on the border town of Kobani.
Around 140,000 Syrian Kurds have already fled to Turkey in the past four days.