In a frame taken from video, U.S. forces patrol Friday on a rural road in northern Syria. (APTV/AP)

Tensions rose Saturday along the Turkish-Syrian border as both Turkey and the United States moved armored vehicles to the region and Turkey’s leader once again demanded that the United States stop supporting Syrian Kurdish militants there.

The relocation of Turkish troops to the area came a day after U.S. troops were seen patrolling the tense border in Syria. Those patrols followed a Turkish airstrike against bases of Syrian Kurdish militia, the United States’ main ally in combating Islamic State militants in Syria.

More U.S. troops were seen Saturday in armored vehicles in Syria in Kurdish areas. Kurdish officials described U.S. troop movements as a “buffer” between them and Turkey.

But Turkey views Syria’s Kurdish People’s Protection group, known as YPG, as a terrorist organization and an extension of the Kurdish militants who have been waging a three-decade-long insurgency against Turkey.

“The YPG, and you know who’s supporting them, is attacking us with mortars. But we will make those places their grave, there is no stopping,” Turkish President Recep Tayyip Erdogan said.

Footage shot Friday night showed a long line of Turkish trucks and military vehicles driving to the border area. The private Ihlas news agency reported that the convoy was heading to southeastern Sanliurfa province from Kilis in the west. The base is 30 miles from Syria’s Tal Abyad, a town controlled by the Kurdish militia.

Just before the troop location, the agency said, Turkish officials announced the completion of a phase of Turkey’s cross-border operation of Euphrates Shield in Syria, adding that the force may be used against Syrian Kurdish militants “if needed.”

Tensions in the border area rose last week when Turkey conducted airstrikes against YPG bases in Syria and Iraq on Tuesday. The Turkish military said that it killed at least 90 militants and wounded scores more. The Kurdish group in Syria said that 20 of its fighters and media activists were killed in the strike, which was followed by cross-border clashes.

Erdogan hinted that his country was also ready to repeat its attacks in Sinjar, Iraq, to prevent it from turning into a base for the Kurdish militia.

Kurdish officials said that the U.S. patrols are monitoring the Turkish-Syrian border to prevent an increase in tensions with Turkey, a NATO member and U.S. ally.

On Saturday, more U.S. troops in armored vehicles arrived in Kurdish areas, passing through the town of Qamishli, close to the border with Turkey. The town is mostly controlled by Kurdish forces, but Syrian government troops hold pockets of territory there, including the airport.

The convoy was followed by another of YPG militia. Some footage posted online showed Kurdish residents cheering U.S.-flagged vehicles as they drove by.

U.S. officials say the troop movement is part of its operations with the Kurdish forces in northern Syria.

Ankara sent its troops into Syria last August in a military operation triggered in large part by the Kurdish group’s expansion along its borders.

The issue has been a source of tension between Ankara and Washington that threatens to hamper the fight against the Islamic State. Instead of working with the Syrian Kurds, Turkey is pressing the United States to let its army join the campaign for Raqqa, the self-proclaimed capital of the Islamic State.

Erdogan is due in Washington on May 16 for his first meeting with President Trump.

Claiming that his country is leading the most effective campaign against the Islamic State, Erdogan said: “Let us, huge America, all these coalition powers and Turkey, let us join hands and turn Raqqa to Daesh’s grave,” using the Arabic acronym for the Islamic State.

The YPG forms the backbone of the U.S.-backed Syria Democratic Forces.

Redur Khalil, spokesman for the YPG in Syria, said that Turkey is reinforcing its border posts opposite Tal Abyad as well as others.

“We hope that this military mobilization is not meant to provoke our forces or for another purpose linked to entering Syrian territories. We don’t want any military confrontation between us, since our priority is to fight Daesh in Raqqa and Tabqa,” Khalil told the Associated Press in cellphone text messages.

Khalil said that his forces were not building up in the area.