German Chancellor Angela Merkel is in Turkey discussing measures to stem the flow of refugees bound for Europe.

Tens of thousands of Syrians remain stranded at the border with Turkey after fleeing a Russia-backed government offensive in Aleppo.

The talks came as reports emerged that another 33 people died off Turkey's coast trying to reach Greece.

Merkel, whose country let in more than a million asylum seekers last year, is holding talks with President Recep Tayyip Erdogan and Prime Minister Ahmet Davutoglu in the Turkish capital on Monday.

 The European Union has promised $3.3bn in aid in return for Ankara's help in stopping the flow of new arrivals on its shores, most of whom make their way through Turkey.

The EU leaders have said that Ankara is obliged to keep its frontiers open to refugees, while also pressing for tighter border controls for those entering Europe.

Turkey's Oncupinar border crossing, which faces the Bab al-Salama frontier post inside Syria, remained closed on Sunday as refugees, mostly women and children, gathered there for a third day waiting for the gate to open.

Al Jazeera's Stefanie Dekker, reporting from Turkey's Kilis province at the Syria-Turkey border, said trucks carrying scaffolding were seen passing through the border on Sunday.

"We know they are building tents and facilities for the thousands of people camped on the other side of the border," she said. 

"But there is no movement on this side. It's very quiet and the border is still closed."

Suleyman Tapsiz, the governor of Kilis province, said that Turkey was taking care of the 30,000-plus refugees who had gathered around the nearby Syrian city of Azaz over the space of 48 hours.

Another 70,000 may head for the frontier if Russian air strikes and Syrian regime military advances continue in Aleppo, he added.

Carrying their few belongings, Syrians queued in the cold and rain in squalid camps waiting for tents the are being distributed by aid agencies, the AFP news agency reported. Others are reportedly sleeping in fields and on roads, it added.

Turkey has vowed to help the crowds of people, including many women and children, but has not opened its borders, and aid agencies have warned that they are facing a "desperate" situation as they wait for help.

President Erdogan said Turkey was ready "if necessary" to let in Syrian refugees trapped on its border.

"The regime has now blocked a part of Aleppo ... Turkey is under threat," Erdogan told reporters on his plane returning from Senegal on Saturday.

"If they reached our door and have no other choice, if necessary we have to and will let our brothers in," he added.

Speaking to Al Jazeera from Gaziantep in Turkey, Fadi Hajjar, a Syrian activist with the Aleppo Media Centre, said there were between 30,000 and 50,000 people waiting at the border.

"This number is likely to increase in the coming days," he said on Sunday.

"Some villages in Aleppo have been completely emptied of people."

Courtesy Aljazeera