Turkey responds to Syrian mortar fire in Akcakale
Turkish artillery has returned fire on Syria for a fifth day after a mortar landed in a border village.
Five people were killed in a similar incident, reportedly in the same street in the village, Akcakale, last week.
Turkey has been firing daily into Syria since Wednesday's deaths, as apparently stray munitions fall on its territory.
In Damascus, a policeman died when a car bomb went off in the car park of the police headquarters in the Syrian capital, state media reported.
The building in the Fahameh area of the city was said to have been damaged in the bombing, described as a "terrorist attack" by the Sana news agency.
Witnesses reported hearing heavy gunfire after the explosion.
During the day, fighting intensified in Syria's second city Aleppo, with fierce battles in two rebel-held neighbourhoods.
AFP news agency reported that warplanes were bombarding the districts of Bab al-Hadid and Shaar.
Syrian forces are also said to be on the offensive in Damascus and Homs.
Meanwhile, unconfirmed reports said rebels had captured a government outpost near the Turkish border province of Hatay.
Clashes in the area in recent days have led to several mortar bombs landing on the Turkish side from Syria, prompting Turkish forces to return fire.
The rebels are fighting to topple Syrian President Bashar al-Assad's government in an uprising that began in March last year.
According to activists, more than 30,000 people have been killed since the uprising against President Assad began. The UN estimates that at least 20,000 have died.
Sunday's shell in Akcakale landed in the grounds of a public building near the centre of the village, but there were no casualties as people had already been evacuated, Turkish NTV said.
Media and local officials said Turkey immediately returned fire. An Associated Press journalist said at least six mortars could be heard.
Wednesday's incident in Akcakale triggered international condemnation.
The UN Security Council said the incident showed the "grave impact" of the Syrian crisis on "regional peace and stability".
Turkey's retaliation was the first time Ankara had taken military action across the border since the Syrian uprising began.
And on the next day, Turkey's parliament authorised troops to launch cross-border operations and strike at Syrian targets for a period of one year.
On Friday, Turkey moved tanks and anti-aircraft missiles into Akcakale, though Turkey's Prime Minister Recep Tayyip Erdogan said his country did not want war.