U.S. Secretary of State John Kerry called Thursday for Syrian and Arab ground troops to take on Islamic State fighters to enable a complete defeat of the organization.

"I think we know it, that without the ability to find some ground forces that are prepared to take on Daesh (IS), this will not be won completely from the air," Kerry told delegates a gathering of dozens of foreign ministers in Belgrade.

Britain joined the US-led bombing campaign over Syria on Thursday, hitting an oil field held by Islamic State jihadists just hours after a decisive parliamentary vote authorized air strikes.

Royal Air Force planes based in Cyprus carried out the "first offensive operation against Daesh terrorist targets inside Syria," the defense ministry said in a statement, using an alternative name for IS.

U.S. Secretary of State John Kerry said Wednesday that Washington welcomed Russia's involvement in efforts to end the Syrian conflict, where Moscow could play an "extremely constructive" role.

"We welcome Russia's engagement in the Syria process. As long as they're focused on Daesh (Islamic State) and as long they are genuine in wanting to be part of implementing the Geneva (accords), they can be an extremely constructive and important player in reaching a solution," Kerry said after NATO talks in Brussels.

Germany wants every European Union state to contribute to a 3 billion euro ($3.2 billion) aid kitty for Syrian refugees in Turkey, saying it is a question of "European solidarity".

"All member states should contribute to the financing totaling three billion euros," Finance Ministry State Secretary Jens Spahn told the daily Sueddeutsche Zeitung in comments confirmed by the government.

Syria looks set to become the latest in several overseas military operations for Britain in recent years, as lawmakers prepare Wednesday to vote to join air strikes against the Islamic State group.

Following the Falklands War in 1982 under then prime minister Margaret Thatcher and the 1990-91 Gulf War, years passed before a series of military engagements ordered by Labor premier Tony Blair under the banner of "humanitarian intervention" and the "war on terror".

President Bashar Assad said peace would only come to war-torn Syria when the West and its Middle Eastern allies "stop supporting terrorists," in an interview aired Tuesday on Czech TV.

Asked what it would take to bring an end to Syria's devastating four-year civil war, Assad said: "When those countries that I mentioned -- France, UK, U.S., Saudi Arabia, Qatar and some other -- stop supporting those terrorists."

Pink was appointed on Monday as UNICEF's newest ambassador, pledging to raise awareness about malnutrition worldwide.

"As a mom myself, it's devastating to know that children are suffering because they don't have adequate nutrition," said the Grammy Award-winning singer.

A deal has been reached for the evacuation of Syrian opposition fighters from the last district under their control in the central city of Homs, the provincial governor told AFP Tuesday.

"We will implement the agreed deal in stages, with 200-300 armed men leaving in the first stage... starting on Saturday," Talal Barazi said.

An operation to resettle 25,000 Syrian refugees in Canada has begun, the International Organization for Migration (IOM) said Tuesday, with 10,000 people due to depart for their new home by the end of the year.

Processing, including security checks, began at a military base in Jordan's capital Amman on Sunday, said Craig Murphy, who briefed journalists in Geneva by phone.

Two Jordanian policemen have died after assailants opened fire on their vehicle while it was on patrol overnight near the Syrian border, authorities said Tuesday.

It was not immediately clear who was behind the attack, which took place in Jordan's northern Irbid governorate bordering war-torn Syria.