Syrians who have been displaced by the ongoing civil war in their country are heading home in larger numbers, according to a Switzerland-based migration agency.

The International Organization for Migration (IOM) said on Friday that nearly 603,000 Syrian refugees set off to return to their cities and villages in the first seven months of this year.

The Syrians included in the figures were returning from other locations in Syria or from Turkey, Lebanon, Jordan and Iraq.

The number nearly matched the 685,662 people who returned during the whole of 2016, Olivia Headon, IOM spokesperson, said.

The returning Syrians were motivated by the desire to protect their homes and possessions; an improved economic and security situation in their areas of origin; as well as problems with integration in their host countries, according to the IOM.

Newly displaced

About 67 percent of the returns this year have been to Syria's Aleppo province, where the opposition-held eastern part of the city was retaken by President Bashar al-Assad's government in December, the IOM said.

But an estimated 808,661 people have been newly displaced this year, "many for the second or third time", Headon said.

Syrians who remain internally displaced number at about 800,000, many of whom have fled violence and strife for the second or third time, according to the IOM.

Syrian government troops recently removed ISIL fighters from their last stronghold in the central province of Homs, recapturing the strategically important town of al-Sukhna after the group took hold of it in May 2015.

ISIL, or the Islamic State of Iraq and the Levant, has suffered military setbacks in recent months, losing ground in Syria and neighbouring Iraq.

Syria's civil war, now in its seventh year, has devastated the country, claimed hundreds of thousands of lives and displaced about half of the prewar population of 22 million.

Jaish al-Islam fighters killed

Also on Friday, a suicide blast in southern Syria near the border with Jordan killed at least 23 fighters of the Jaish al-Islam group, according to a monitoring group.

The Syrian Observatory for Human Rights (SOHR) said the bomber detonated an explosive belt at a base used by the fighters near the Nasib border crossing.

"Most of the 23 killed were from Jaish al-Islam. Dozens were wounded, including 20 in critical condition," said Rami Abdel Rahman, SOHR's head.

There was no immediate claim of responsibility.

The Nasib border crossing - known as Jaber on the Jordanian side - lies in Syria's southern Deraa province and was captured by armed groups in April 2015.

For its part, Turkey says new precautions are being taken along its border in response to recent developments in northwestern Syria.

Speaking after Friday prayers in Ankara, Binali Yildirim, Turkey's prime minister, said "radical groups have taken over control" in Syria's Idlib province.

Last month, al-Qaeda-linked Hayet Tahrir al-Sham - Arabic for Levant Liberation Committee, also known as HTS - captured the majority of Idlib after battles with the Ahrar al-Sham group.

HTS also seized the Bab al-Hawa border crossing with Turkey's Hatay province.

"We are taking the necessary precautions in Hatay's 150km border with Syria," Yildirim said, in order to prevent "humanitarian dramas" and threats against Turkey.

Turkey's President Recep Tayyip Erdogan said on Friday that talks on the situation in Idlib are ongoing between the country's intelligence service, Iran and Russia.