'Pause' in fighting in Syria between Turkish and Kurdish forces appears to be in jeopardy

Turkey's agreement with the United States to "pause" fighting in Syria appears to have been breached within hours of Vice President Mike Pence's announcement as eyewitnesses report violence is still ongoing.

Turkish artillery continued shelling Ras al-Ayn, a Syrian city on the Turkish border that had been facing heavy violence since U.S. troops withdrew early last week, according to eyewitnesses.

Eyewitness reports said shelling continued in the city through Thursday night and into Friday morning.

Syrian Democratic Forces (SDF), which is made up of many members of the Kurdish People's Protection Units (YPG), had also not withdrawn from Ras al-Ayn, which was part of the agreement between Turkey and the U.S.

"Clashes in the key town of Ras al-Ayn have continued and Kurdish officials say Turkish artillery fire is still pounding its main hospital," ABC News' James Longman reported from northern Iraq. "The Kurds say Turkey never stopped its bombardment, so their fighters will not leave the area. Thousands are still on the move trying to escape this violence."

Turkish President Recep Tayyip Erdogan denied clashes were ongoing on Friday.

"I don't know where you're getting your news from. According to the news I received from my defense minister, there is no question of clashes. These are all speculation, disinformation," he told reporters.

Kurdish activists said that a medical convoy is headed toward the city Friday to help evacuate injured people and provide needed medical equipment and supplies to aid stations.

An Associated Press journalist on the Turkish side of the border reported seeing columns of smoke from shelling rising from Ras al-Ayn on Friday morning, which images also showed.

President Donald Trump tweeted early Friday afternoon that he had "just" spoken with Erdogan, who told him "there was minor sniper and mortar fire that was quickly eliminated."

"He very much wants the ceasefire, or pause, to work. Likewise, the Kurds want it, and the ultimate solution, to happen," Trump continued.

He added in subsequent tweets that "there is good will on both sides" and that the "U.S. has secured the Oil & the ISIS Fighters are double secured by Kurds & Turkey."

Pence had announced on Thursday that the agreement between Turkey and the U.S. stated there would be a 120-hour "pause" in operations by Turkey, giving Kurdish forces time to withdraw from a 20-mile-deep "safe zone" on the Turkish-Syrian border to be controlled by Turkey.

The vice president initially called this agreement a ceasefire, but Turkish Foreign Minister Mevlut Cavusoglu said it was a "pause in Turkey's operation" and "not a ceasefire."

It was unclear Thursday whether the SDF had agreed to the deal.

Gen. Mazloum Ebdi, the SDF's commanding general, has requested an emergency call with Pence to request American help to collect proof Turkey is violating the pause, a senior official told ABC News.

Erdogan said Friday that Kurdish fighters had begun pulling out, but he added that Turkish soldiers would remain in the northeast to confirm they were leaving. Should they not leave, Erdogan said, Turkey would restart operations.

When asked Thursday what will happen to the Kurdish forces who lived in cities and towns in what is now supposed to be Turkish-held territory, Pence instead touted the importance of the safe zone in achieving peace.

"We believe that the Kurdish population in Syria -- with which we have a strong relationship -- will continue to endure," he said.

ABC News' Matt McGarry, Conor Finnegan, Rashid Haddou and Martha Raddatz contributed to this report.