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The Associated Press
This photo released on Sunday, May 17, 2015, by the Syrian official news agency SANA, shows the general view of the ancient Roman city of Palmyra, northeast of Damascus, Syria. A Syrian official said on Sunday that the situation is "fully under control" in Palmyra despite breaches by Islamic State militants who pushed into the historic town a day earlier. (SANA via AP)

BEIRUT — Islamic State militants seized parts of the ancient town of Palmyra in central Syria on Wednesday after fierce clashes with government troops, renewing fears the extremist group would destroy the priceless archaeological site if it reaches the ruins.

The Britain-based Syrian Observatory for Human Rights said the militants gained control of as much as a third of the town in heavy clashes during the day. Palmyra is home to a UNESCO World Heritage Site and is famous for its 2,000-year-old majestic Roman colonnades.

The majority of the ruins are located in Palmyra's south, and the militants entered Wednesday from the north after seizing the state security building from government forces. But their presence has sparked concerns they would destroy the ruins as they have done with major archaeological sites in neighboring Iraq.

Following setbacks in both Syria and Iraq, Islamic State fighters appear to have gotten a second wind in recent days, capturing Ramadi, capital of Iraq's largest Sunni province, and advancing in central Syria to the outskirts of Palmyra.

In Iraq, thousands of displaced people fleeing from Ramadi and the violence in the western Anbar province poured into Baghdad Wednesday after the central government waived restrictions and granted them conditional entry, a provincial official said.

The exodus is the latest in the aftermath of the fall of the city of Ramadi — the Anbar provincial capital — to the Islamic State over the weekend. The Shiite-led government in Baghdad is struggling to come up with a plan to reverse the stunning loss of the city, pledging a counter-offensive and relying on Iranian-backed Shiite militiamen to join the battle for Ramadi.

Athal al-Fahdawi, an Anbar councilman, said that thousands of civilians from Ramadi who were stranded on open land for days, are now being allowed to cross a bridge spanning the Euphrates River and enter Baghdad province.

On Tuesday, Anbar local officials said five of the displaced residents died from exhaustion in Bzebiz area, where the displaced had been forced to stay as they were kept away from Baghdad.

According to the International Organization for Migration, more than 40,000 people have been displaced from Anbar province since Friday, when IS conquered Ramadi. In the past, people fleeing Anbar have been prevented from entering Baghdad due to fear that militants might mingle in with the crowds and sneak into the Iraqi capital.

Meanwhile, residents still left in Ramadi told The Associated Press over the phone on Wednesday that Islamic State militants were urging them over loudspeakers not to be afraid and to stay in the city, already suffering from acute shortages of food and medicines. However, IS fighters were not preventing those wanting to leave the city to go, the residents said, speaking on condition of anonymity for fear for their own safety.

It is still unknown when the expected wide-scale operation to recapture Ramadi and other cities will start.

Baghdad officials and leaders of the so-called Popular Mobilization Units, which consists of a number of Shiite militias who are fighting on the side of the Iraqi military and security forces, have repeatedly said they need time for a military buildup and reconnaissance.

When the Islamic State launched its blitz last year and entire cities and towns fell into the hands of the militants, the Iraqi government at first took only defensive measures and in many cases, soldiers and Iraqi forces abandoned their posts and fled in the face of the IS assault.

Military operations to retake entire swaths of Iraq that had fallen to IS began only months later. The U.S. launched its airstrikes campaign in August.

Yacoub reported from Baghdad.