KILIS, Turkey (AP) — Turkey has reached the end of its "capacity to absorb" refugees but will continue to take them in, the deputy premier said Sunday, as his country faced mounting pressure to open its border to tens of thousands of Syrians who have fled a government onslaught.

Turkish authorities say up to 35,000 Syrians have massed along the border, which remained closed for a third day on Sunday. The governor for the Turkish border province of Kilis said Saturday that Turkey would provide aid to the displaced within Syria, but would only open the gates in the event of an "extraordinary crisis."

Deputy Prime Minister Numan Kurtulmus told CNN-Turk television that Turkey is now hosting a total of 3 million refugees, including 2.5 million Syrians.

"Turkey has reached the end of its capacity to absorb (refugees)," Kurtulmus said. "But in the end, these people have nowhere else to go. Either they will die beneath the bombings and Turkey will ... watch the massacre like the rest of the world, or we will open our borders."

Kurtulmus said some 15,000 refugees from Syria were admitted in the past few days, without elaborating. He put the number of refugees being cared for on the other side of the border at 30,000.

"At the moment, we are admitting some, and are trying to keep others there (in Syria) by providing them with every kind of humanitarian support," Kurtulmus added. "We are not in a position to tell them not to come. If we do, we would be abandoning them to their deaths."

He did not explain why the Turkish border gate at Oncupinar, opposite the Bab al-Salameh crossing in Syria, was being kept closed or why tens of thousands of refugees were not immediately being let in.

In Syria, pro-government forces pressed ahead with their offensive in the northern Aleppo province, which has caused the massive displacement of civilians toward the Turkish border. Syrian opposition activists said Syrian ground troops backed by Russian airstrikes were engaged in intense fighting with insurgents around the village of Ratyan and surrounding areas north of Aleppo city.

The Britain-based Syrian Observatory for Human Rights and Kurdish officials said the main Kurdish militia in the Kurdish enclave of Afrin, north of Aleppo, was taking in some of those stuck on the border.

The army has almost fully encircled Aleppo, Syria's largest city and one-time commercial center, preparing the way for a blockade. The main supply line to the Turkish border has already been cut and many residents of the city were looking to leave, anticipating severe shortages in coming days.

Dr. Ahmad Abdelaziz, of the Syrian American Medical Society, a humanitarian organization, said there were only four general surgeons for the entire city.

"The people there are very worried there could be a siege at any time. We expect a lot of people to get out of the city if the situation remains like this, if there is no improvement," he said.

Abdelaziz, who goes in and out of Aleppo but spoke to the AP from the Turkish city of Gaziantep, described a dire scene at the border and said it was difficult to get medicine to the people gathered there.

"There are so many old people and children in the cold weather... They are surrounded by ISIS from the east, the regime from the south and Kurdish forces from the west," he said, using an acronym for the Islamic State group.

On Saturday, the European Union urged Turkey to open its borders at a meeting in Amsterdam, saying it was providing aid to Ankara for that purpose. EU nations have committed 3 billion euros ($3.3 billion) to Turkey to help refugees, part of incentives aimed at persuading Turkey to do more to stop thousands of migrants from leaving for Greece.

Kurtulmus estimated that "in the worst case scenario" as many as 1 million more refugees could flee the Syrian city of Aleppo and surrounding areas.

The Syrian uprising began in March 2011 with mostly peaceful protests but escalated into a full-blown civil war after a harsh government crackdown. The fighting has killed more than 250,000 people and forced millions to flee the country.

Pope Francis weighed in Sunday with a public plea for aid to Syrians fleeing civil war so that their survival and dignity are assured.

"I am following with strong worry the dramatic fate of the civilian population caught up in the violent combat in Syria and forced to abandon everything to flee the horrors of the war," Francis told a crowd in St. Peter's Square on Sunday.

The pope called upon the international community to spare no efforts to revive negotiations to end the war that began in 2011. The latest round of Syrian peace talks recently stalled.

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Fraser reported from Ankara, Turkey. Associated Press writers Dominique Soguel in Istanbul and Zeina Karam in Beirut contributed to this report.