Haidar Houri, a Syrian refugee who feels like he missed out on his chance to migrate to Europe, sits in a hotel lounge in Gaziantep, Turkey on April 15. (Hugh Naylor/The Washington Post)

Hussein Taysoun once saw opportunity in the great migration to Europe. Now, the 34-year-old Syrian feels trapped.

An agreement between the European Union and Turkey to halt the extraordinary flow of asylum seekers and economic migrants to the continent has all but slammed shut the Turkey-to-Greece smuggling gateway. For Syrians who made it only as far as southern Turkey, the future looks bleak.

Rights groups and aid workers say Turkish authorities have subjected refugees to arbitrary detentions and deportations. After fleeing hardship in their countries of origin, others here have found it a struggle to scrape by.

Many such as Taysoun — who is one of nearly 3 million Syrians offered refuge in Turkey — now feel they missed their chance.

“It’s like we have no more options left — except to suffer,” said Taysoun, who arrived in Gaziantep, a city near the border with Syria, three years ago and supports his family by working in construction.

Qusay Suleibi fled his home town of Palmyra, Syria, after the Islamic State briefly took over last year. He now works at a cafe in the Turkish city of Gaziantep. (Hugh Naylor/The Washington Post)

Like the vast majority of Syrians in Turkey, Taysoun lacks a formal work permit, increasing his chances of being exploited by employers, rights groups say. Freelance construction pays $15 dollars a day — that is, he said, if he can land a job and if contractors actually pay up. He hasn’t found work in weeks, forcing him to consider moving back to his war-torn country.

“Syria is cheap,” he said.

In his dimly lighted basement apartment of cinder-block walls and hopelessness, Taysoun said he regretted that he did not join the more than 1 million people smuggled on dinghies to Greek islands over the past year and a half.

Europe, he said, would afford his family possibilities. Jobs. Education. Hope.

But he had hesitated, fearing the perilous boat ride that has taken hundreds of lives. He also had trouble raising enough money for smuggling fees.

Now, that journey seems like a non-starter.

Under the E.U.-Turkey deal, which was struck last month, refugees arriving in Greece by smuggling boat are escorted onto ferries and sent back to Turkey.

In exchange, Turkey receives billions of dollars and other incentives, including relaxed visa requirements for its citizens to travel to Europe and a resumption of talks to bring Turkey into the E.U.

Observers say the agreement seems to have had the intended effect. The number of people attempting the journey from Turkey’s coast has plummeted, and hundreds of mostly Afghans, Bangladeshis and Pakistanis have been returned to Turkey.

But Human Rights Watch, Amnesty International and other rights groups have criticized the deal, accusing Turkish authorities of preventing rights workers and the United Nations from visiting facilities that hold refugees and migrants.

Moreover, they say that Turkey has been rounding up refugees and deporting them without granting proper asylum procedures. And they warn that non-Syrian asylum seekers — notably Europe-bound people fleeing conflicts in Iraq and Afghanistan — lack protections in Turkey because of laws that do not meet international human rights conventions.

All of this, critics say, calls into question a fundamental assumption of the E.U.-Turkey deal: that it is safe to return refugees detained in Greece to Turkey.

“It’s very easy for this to become all about criticizing Turkey, but it’s quite clear that this is being driven by the E.U.,” said Rae McGrath, senior director for migration response at Mercy Corps.

Turkey was already shouldering an incredible burden before the agreement, hosting nearly three times as many Syrian refugees as the number of migrants and asylum seekers who made their way to Europe over the past 15 months.

A senior Turkish official denied the allegations of abuse. He listed Turkish support for Syrians that includes special protections and a long list of humanitarian programs worth $10 billion.

“Unfortunately, the international community, including U.N. agencies, contributed less than $500 million” for Syrians in Turkey, said the official, who spoke on the condition of anonymity because he lacked the authorization to discuss the topic publicly.

Still, Qusay Suleibi worries that Turkish patience has run thin. The 25-year-old recalled wanting to go to Europe, but his family back in Syria urged him to stay put in southern Turkey. They would eventually be reunited in Turkey, or so he thought.

In recent months, Turkey started requiring visas for Syrians and blocking most entries, including Suleibi’s mother and siblings. “I’m not sure what I can do now, because I can’t go back to Palmyra,” he said of his home town, which he fled after Islamic State militants stormed it last year. Although the Syrian government has reclaimed the city, he has no desire to return.

In Gaziantep, he makes sandwiches at a Syrian-run restaurant, where he works 12-hour days, sleeps in a crowded employee dormitory upstairs and hardly ever leaves. He fears that police could stop him for lacking a residency permit.

Even as he doubts whether he will ever set foot in Europe, other employees at the restaurant are saving money for the journey.

“I’ve got $700 saved now!” said Mohammed al-Hammad, a 27-year-old also from Palmyra.

He spoke about finding an alternative route via Libya, which aid organizations predict more refugees will take because of the E.U.-Turkey deal.

But Taysoun, the construction worker, seems to have given up on Europe. He wonders whether he can continue to pay his monthly rent of $80. If he can’t, he said, he might move his family to camps for internally displaced Syrians back across the border.

Prevented from entering Turkey, tens of thousands of Syrians have crammed into the camps, where they receive support from aid groups but have faced attacks by the Islamic State.

But residents don’t pay rent, Taysoun pointed out.

“Right now, I have to focus on how to feed my children,” he said.

Zakaria Zakaria contributed to this report.