Turkey 'has duty' to defeat Islamic State group in Syria.

Turkey has a duty to defeat the so-called Islamic State (IS) in neighbouring Syria, President Recep Tayyip Erdogan has said.

He called it a "binding duty", to ensure the militants were "unable to carry out actions inside our country".

Turkey's military said its warplanes killed 20 IS fighters during air raids over Syria on Saturday.

A 10-day truce is due to start in Syria on Monday, followed by co-ordinated air strikes against jihadist militants.

The cessation of hostilities was agreed on Friday between the US and Russia, which is an ally of Syria's President Bashar al-Assad.

• What's left after five years of war?

• Why is there a war in Syria?

• Ten more years of war?

Mr Erdogan said in a statement that the current Turkish military operation in Syria, known as Operation Euphrates, was just a "first step" in the fight against IS, which he calls Daesh.

"It is our duty to our people to finish off Daesh in Syria, and to bring them to a level where they can't carry out attacks in our country," he said.

In the same statement, he said Turkey was also determined to defeat the outlawed Kurdish Workers' Party (PKK) and the Feto group of US-based cleric Fethullah Gulen.

Mr Erdogan has accused Mr Gulen of masterminding a failed coup attempt in July.

"We are determined to wipe out the PKK trouble from Turkey together with our security forces. Just like Feto, the PKK stands no change against our sagacious people and the power of our state."

John Kerry: "If this arrangement holds then we will see a significant reduction in violence across Syria"

Russia and the US will then establish a joint centre to combat jihadist groups, including IS and Jabhat Fateh al-Sham (known until recently as the Nusra Front).

The conflict in Syria, which began with an uprising against Mr Assad, has raged for five years and claimed the lives of more than a quarter of a million people.

Millions have fled abroad, many of them seeking asylum in the EU, but nearly 18 million people remain in Syria, which has been carved up by fighting between government and rebel forces.

Jihadist groups like so-called Islamic State and Jabhat Fateh al-Sham (formerly known as Nusra Front) face the joint might of the Russian and US air forces

Moderate rebels and civilians in the areas they hold will no longer face the threat of indiscriminate air strikes such as barrel-bombing although the Syrian air force will not be grounded completely; aid deliveries will be allowed to areas currently under siege

President Assad will be in a stronger position as the US and Russia engage two of his most effective military opponents while moderate rebels observe the truce with his forces

February 2012: Syrian government "categorically rejects" an Arab League plan calling for a joint Arab-UN peacekeeping mission

• Syria rejects new Arab League peace mission proposal

June 2012/January 2014/January 2016: Three failed UN-sponsored peace conferences in Geneva

• What is the Geneva II conference on Syria?

September 2013: Kerry and Lavrov negotiate a deal to strip the Syrian government of its chemical weapons in return for the US backing away from air strikes. Since then, the government has again and repeatedly been accused of using toxic chemicals against rebel-held areas

• Syria civilians still under chemical attack

February 2016: World powers agree in Munich on a nationwide "cessation of hostilities" in Syria excluding jihadist groups. There is no agreement on any joint US-Russian operations. The "pause" quickly unravels as Assad promises to regain control of the whole country

• Syria war pause plan agreed by world powers

March 2016: President Vladimir Putin declares "mission accomplished" in Syria and orders removal of "main part" of Russia's air army in Syria. Russian air strikes have continued ever since

• Putin orders 'main part' of forces out

The Mariana DAngelo Editorial Group