Turkey is reportedly deporting Syrian refugees from Istanbul to Syria, including to the volatile northwest province of Idlib, in a campaign launched recently against migrants who lack residency papers.

The crackdown comes at a time of rising rhetoric and political pressure on Turkey’s 3.6 million registered Syrian refugees to return home.

Some estimates says hundreds of thousands of unregistered Syrians are living Turkey, many in urban areas such as Istanbul. 

Refugee rights advocates say the deportations violate international law, which prohibits forcing people to return to a country where they are still likely to face persecution or risk to their lives.

Arrests reportedly in mid-July, with police officers conducting spot-checks in public spaces, factories, and metro stations around Istanbul and raiding apartments.

According to UAE-based news site The National, as word spread in Istanbul’s Syrian community, many people shut themselves up at home rather than risk being caught outside.

It is not clear how many people have been deported so far, with estimates ranging from hundreds to a thousand.

Turkey’s Ministry of Interior has said the arrests are aimed at people living without legal status in the country’s most populous city.

Istanbul authorities have said that only “irregular migrants entering our country illegally [will be] arrested and deported.”

The authorities said that Syrians registered outside Istanbul would be obliged to return to the provinces where they were first issued residency. 

Human Rights Watch said in a statement that the “deportation of Syrians to their country, which is still in the midst of armed conflict, is a clear violation of both Turkish and international law,” including the “return of Syrians without temporary protection cards”.

Since 2014, Syrian refugees in Turkey have been registered under “temporary protection” status, which grants the equivalency of legal residency and a work permit.

Those with temporary protection need special permission to work or travel outside of the area where they first applied for protection.

But last year, several cities across the country – including Istanbul – ceased registering newly arrived Syrians.

The Turkish government says that Syrians have been deported only to the rebel-held areas of northern Aleppo, where the Turkish army maintains a presence alongside groups that it backs.

But refugee rights groups say many have been sent back to Idlib, currently the target of a deadly air offensive by the Syrian air force, back by their Russian allies.

The offensive that began in late April sparking an upsurge in fighting, killing more than 400 civilians and forcing more than 330,000 people to flee their homes.

Human Rights Watch and other organisations have reported that Turkish security forces regularly intercept and return Syrian refugees attempting to enter the country.

As conflict rages in and around Idlib, more and more people are still trying to get into Turkey. 

Turkey said late last year that more than 300,000 Syrians had returned to their home country voluntarily.

Human rights groups say a failed coup attempt against President Recep Tayyip Erdoğan in July 2016 led to an emergency decree that was used to arrest individuals whom the government perceived as opponents.

Parts of that decree were later legislated, making it easier for authorities to deport foreigners on the grounds that they are either linked to terrorist groups or pose a threat to public order.