Syria, Turkey Trade Fire; Blast Hits Damascus Police

Turkish troops guard a border crossing in Akcakale, across from Syrian rebel-controlled Tel Abyad, on Sunday.

Syria and Turkey exchanged artillery fire for a fifth straight day on Sunday, while insurgents struck police headquarters in Damascus, in the third high-profile attack in the Syrian capital in recent weeks.

The escalating pressure in the capital and along the border present a rising pair of challenges for the Assad regime, which already accuses outside forces, including Turkey, of working with the rebels to destabilize the country.

A bomb in the Damascus police headquarters' parking lot caused the powerful blast that killed a police officer, said an official at the interior ministry.

In Turkey, there were no immediate reports of casualties in the early afternoon after a shell landed close to a grain-storage facility, witnesses said, several hundred yards from the town center in Akçakale, the border town where Syrian artillery killed five Turkish citizens on Wednesday.

Turkey's military fired artillery on targets inside Syria in response, Turkey's state-run news agency reported.

It has fired artillery shells across the border every day since Wednesday in response to Syrian artillery hitting towns along its border.

Syria's government, despite international condemnation, has held back from apologizing to Turkey while it investigates the source of the fire from its territory, which it says could be from antigovernment fighters who control large parts of the border territory.

U.S. Defense Secretary Leon Panetta warned over the weekend that the continued exchange of fire across the Syrian-Turkish border raises concerns that the conflict could spread to neighboring countries.

Mr. Panetta, in a news conference in Peru on Saturday, said that the U.S. is using its diplomatic channels to relay worries about the fighting, the Associated Press reported.

Still, regional diplomats and analysts say the risk of a full-blown confrontation between Syria and Turkey, former allies whose leaders were personal friends before Syria's crisis erupted last year, is limited.

Cross-border incidents are likely to continue, however, analysts say, as President Bashar al-Assad's forces pursue rebel fighters leading an insurgency against his rule.

"The risks of miscalculation are considerable," Ayham Kamel and Naz Masraff, analysts with political-risk firm Eurasia Group, wrote in a recent note.

"Ankara and Damascus no longer share a direct and open military or political communication channel. During potential clashes, miscommunication is probable and both sides could misinterpret their respective intentions," they wrote.

Mr. Assad can't afford to give up control of the border area, a lifeline for rebels, and has delegated military decision-making to local commanders, the analysts said. That raises the risk of knee-jerk responses and potential mistakes that could escalate, they added.

Turkey's leadership has made clear that it has no intention to go to war with Syria but that it would respond to violations of its sovereignty.

Turkish Prime Minister Recep Tayyip Erdogan has raised doubts over whether the frequent cross-border fire from Syria is an accident but has refrained from further comment on the Syrian government's intentions.

In Syria's al-Raqqa province, just across the border from Akçakale, rebel fighters said the source of the shelling on Sunday that struck Turkish territory was government tanks in the village of Ain Arous, about seven miles from the border.

The nearby city of Tal Abyad was still being shelled by Syrian army positions in the area, residents said.

Syrian rebels have voiced frustration with what they see as a restrained response from Turkey, but rejected accusations that they might be instigating border tensions to push Turkey toward an armed confrontation with Syrian regime forces of the sort that rebels have long advocated.

"The Free Syrian Army in Tal Abyad doesn't have tanks or missiles to launch these kind of attacks anyway," said Ayham al-Khalaf, an activist with the local activist media council in al-Raqqa.

In Damascus, security checkpoints cordoned off the Fahama district in the capital's center after the bombing occurred shortly after 7:15 p.m. local time.

A few reporters were later allowed into the compound where cleaning crews were sweeping up the debris and distraught members of the police force were comforting each other.

The facade of the two-story building was torn away and more than 20 vehicles were either incinerated or badly damaged. The stench of gasoline from ruptured fuel tanks filled the air.

Several police officers said a driver for one of the senior officers placed the bomb inside his boss's car, detonated it, and fled.

"He blew up the car and ran away to Deraa,"—the city in southern Syria where antigovernment protests first erupted last year—said a young officer with a bandaged arm and blood-covered T-shirt.

The bombing is the latest in a string of apparent rebel victories in the heart of Damascus, signaling how precarious security has become in the once-calm capital even as fighting between government and rebel forces has been focused farther north in Aleppo.

Sunday's attack came after several bombings last week in Aleppo that appeared to target hotels housing military officers, and blasts that rocked the headquarters of the armed forces in central Damascus on Sept. 26.

Police chief Maj. Gen. Ibrahim Ibrahim sat on a lawn chair at the scene of the blast in Damascus but refused to speak to the media.

An hour after the first explosion, two other explosions were heard in the city, but their cause wasn't immediately known.