U.S. Secretary of State Hillary Clinton is warning Syria to pull its troops back from the border with Turkey, saying their presence is worsening an already bad situation for refugees and risks sparking border clashes with the Turks.

Clinton told reporters in Washington Thursday that the U.S. sees the situation as worrisome and that the Syrian military should immediately end attacks and provocations in the region. She said the buildup of soldiers near the Turkish border is another sign of the Syrian government's intent to repress its own people.

Early Thursday, Syrian troops backed by tanks and snipers stormed the border town of Khirbet al-Jouz, sending hundreds more refugees fleeing into Turkey.

Syria's deployment is the closest its troops have come to neighboring Turkey since the military operation in the area began two weeks ago. Turkish troops moved their border positions several hundred meters back, apparently to avoid potential confrontations with Syrian units.

The president of the Turkish Red Crescent, Tekin Kucukali, said more than 600 new refugees had crossed into Turkey by midday Thursday. Most arrived in a convoy of about 20 minibuses, while others rushed on foot across the border.

Kucukali, who spoke to reporters in the border town of Guvecci, said the Red Crescent is trying to meet the needs of more than 11,000 Syrian refugees, many of whom described fleeing the sound of gunfire and advancing tanks. He said an estimated 17,000 more displaced Syrians have massed along the border, poised to flee.

The two countries' foreign ministers discussed the situation in Syria and the refugee issue by telephone, and Syria's ambassador to Ankara was later summoned to the Foreign Ministry.

The uprising against Syrian President Bashar al-Assad reached its 100th day Thursday. Activists say Syria's crackdown has killed at least 1,400 people.

Also Thursday, the European Union hit Syria with new sanctions, adding another seven individuals to a list of people and entities under an EU asset freeze and travel ban.

Three of the individuals are Iranians, who along with other newly-targeted individuals and companies are suspected of providing military equipment and support to the Syrian government.

Syrian Foreign Minister Walid Moallem on Wednesday denounced EU sanctions, saying they represent an “act of war.”

Speaking at a news conference in Damascus, he said Syria “will forget Europe is on the map.” He also denied that Iran and Lebanon's Hezbollah are helping Syria's government to crack down on the unrest.

Mr. Assad said this week he is willing to hold a national dialogue on possible reforms to parliamentary election laws, the media and Syria's constitution.

United Nations Secretary-General Ban Ki-moon said the offer does not have “much credibility” because the crackdown is continuing. Mr. Ban said U.N. Security Council action on the Syria crisis would be “helpful.”

Western powers also have dismissed Mr. Assad's comments.