A picture released May 22 on an Islamic State website purports to show the Islamic State flag, top center, raised above an ancient castle in the Syrian town of Palmyra. (AP)

The Syrian army is deploying troops in areas near the ancient city of Palmyra in apparent preparation for a counterattack to retake it from the Islamic State militant group, an official said.

Gov. Talal Barazi of the central province of Homs, which includes Palmyra, said Sunday that Islamic State fighters have “committed mass massacres in the city of Palmyra” since they captured it Wednesday. He said militants took many civilians, including women, to unknown destinations.

Activists in the region have said that the extremists have hunted down President Bashar al-Assad’s loyalists since taking the city, killing about 280 people.

Barazi said troops are fighting with militants in the nearby Jizl area. “There are plans, but we don’t know when the zero hour for a military act in Palmyra” will come, he said.

The capture of Palmyra has stoked fears that the militants might try to destroy one of the Middle East’s most spectacular archaeological sites — a 2,000-year-old Roman-era city on the modern town’s edge — as they have destroyed others in Syria and Iraq.

In Qatar, the European Union’s foreign policy chief said the recent conquest of Palmyra and the Iraqi city of Ramadi by the Islamic State only increases the need for greater political cooperation in the face of the militant threat.

“Only a political solution both in Syria and Iraq can provide a settlement for the crisis,” Federica Mogherini said after a meeting between officials from the European Union and the six-nation Gulf Cooperation Council.

Meanwhile, the leader of the Lebanese Shiite militia Hezbollah said Sunday that the region is facing “unprecedented danger” from extremist groups and he pledged that his fighters will expand their involvement in Syria’s civil war in support of government forces.

Hasan Nasrallah spoke during a ceremony marking the 15th anniversary of Israel’s withdrawal from southern Lebanon, vowing to battle Sunni extremist groups such as the Islamic State and al-Qaeda.

Hezbollah openly joined Assad’s forces in the civil war in 2013, and its fighters have been taking part in a major battle in recent weeks against extremists in the Qalamoun Mountain region.

“Our presence will grow whenever it is required for us to be present,” Nasrallah said Sunday.

Inside Syria, a military helicopter crashed earlier Sunday at the northern air base of Kweiras, killing its crew, state TV said. An activist group said it was shot down by Islamic State militants.

The TV report quoted a military official as saying that the helicopter crashed because of a technical problem while taking off.