U.S. troops to help protect Turkey from Syrian missiles

NEW: At least 80 people were killed across Syria on Friday, an opposition group says For a third day, rebels tried to wrest control of a helicopter base from government forces Parents of a kidnapped U.S. journalist in Syria are pleading for his release An explosion at a gas station in Damascus killed 10 people

(CNN) -- U.S. troops arrived in Turkey on Friday to man Patriot missile defense batteries near the Syrian border, according to Turkish state media.

Syria has previously launched Scud missiles at cities near the Turkish border in a desperate bid to extend its firepower.

In response, the U.S., Germany and the Netherlands deployed Patriot air defense missiles to the border region to intercept any Syrian ballistic missiles.

Read more: U.S. officials: Syria using more accurate, Iranian-made missiles

The missiles and troops will be under the overall control of NATO, but the missiles will be operated by U.S. forces

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A group of 27 U.S. troops landed in Gaziantep, Turkey, where they will survey the Patriot deployment, according to Turkish state news agency Anadolu.

U.S. officials did not release any information about the troops' arrival, but had said last month that forces would be deployed to Turkey.

"We've made very clear to them that we're going to protect countries in this region," Defense Secretary Leon Panetta said last month. "We have to act to do what we have to do to make sure that we defend ourselves and make sure that Turkey can defend itself."

The fight for a helicopter airport

Taftenaz air base in northern Syria has been a deadly thorn in the side of rebels for months.

For the third day, Free Syrian Army fighters tried to wrest control of the helicopter base from government forces.

If successful, the assault would shut down President Bashar al-Assad's military helicopter pads and diminish his airstrikes in the region.

Both opposition and government sources reported that the extremist Nusra Front, which the U.S. has designated as a terrorist group, is taking part in the assault on the airport.

Al-Assad has exacted retribution on the nearby city of Binnish, where amateur video shows dozens of smoke plumes marking the spots where deadly ordnance has struck.

Read more: Getting to know Syria's first family

On Thursday, rebels published videos of themselves firing on the air base with heavy truck-mounted machine guns and a captured tank, destroying one government tank and appearing to shoot down a helicopter.

CNN cannot confirm the authenticity of videos from the Syrian conflict posted online.

Read more: Patriot missiles a warning to Syria's al-Assad

Gas station attack in Damascus

An explosion at a gas station in Damascus near a hospital killed 10 people Friday, Syrian TV reported.

An opposition organization expects the toll to rise as many of the injured are in critical condition after fire spread to nearby cars and buildings.

The explosion came from a car bomb, the Syrian Observatory for Human Rights posted on its Facebook page.

Read more: What's next for Syria

Appeal for missing U.S. journalist

A picture taken on November 5 in Aleppo shows U.S. freelance reporter James Foley,

In New Hampshire, the parents of American journalist James Foley appealed Thursday to his kidnappers to release him and inform them of his whereabouts and condition of his health.

Read more: American journalist abducted in Syria

Foley's father choked up while reading a statement directed at the abductors. "We'd like them to contact us," he said. "I ask the captors for their compassion and James' quick release."

Foley was abducted in November in Syria, where he has worked for a year. He had been detained before while working in Libya but was later released by the government.

Read more: Missing American journalist's parents: Send our son home

The rapidly mounting death toll

At least 80 people were killed across Syria on Friday, according to the Local Coordination Committees of Syria, an opposition activist network. CNN cannot independently confirm those numbers.

The overall death toll in devastated Syria has surpassed an estimated 60,000 people, the United Nations said Wednesday.

To put it in perspective: 60,000 people is roughly the population of Terre Haute, Indiana; or Cheyenne, Wyoming. It's how many people would fit in Dodger Stadium, and it's more than the 50,000-plus U.S. combat deaths in Vietnam.

Read more: U.N.'s Syria death toll jumps dramatically to 60,000-plus

The figure is about 15,000 higher than the death toll CNN had cited from a collection of sources.

On Thursday, al-Assad's forces repeatedly bombed the Damascus suburb of Douma with airstrikes. In videos posted on the Internet, residents combed through rubble, pulling out the bodies of those killed.