Turkey's military struck targets inside Syria today in response to a mortar bomb fired from Syrian territory which killed five Turkish civilians, prime minister Tayyip Erdogan's office confirmed tonight
"Our armed forces in the border region responded immediately to this abominable attack in line with their rules of engagement; targets were struck through artillery fire against places in Syria identified by radar," a statement from Mr Erdogan's office said.
"Turkey will never leave unanswered such kinds of provocation by the Syrian regime against our national security."
A woman and her three daughters were killed in Akcakale today along with another woman, state-run Anatolia news agency reported, citing local authorities.
Sanliurfa Province governor Celalettin Guvenc said three or four Syrian shells fell in the border town. Hundreds of residents marched to the local governor's office after the incident, demanding the resignation of town authorities, CNN-Turk said.
United Nations secretary-general Ban Ki-moon called on Syria to respect the "territorial integrity of its neighbours" after the incident.
Syrian leaders have blamed Turkey for aiding rebels who are fighting to oust president Bashar al-Assad. The Turkish government, which hosts about 94,000 Syrian refugees, has allowed some opposition fighters to use the country as a base.
US secretary of state Hillary Clinton told reporters in Washington that "we are outraged" by the attack and called the situation in Syria "very, very dangerous."
Ms Clinton said she plans to speak by phone with Turkish foreign minister Ahmet Davutoglu today.
Turkey's deputy prime minister Bulent Arinc, without elaborating, said today that members of Nato have responsibilities in the "face of such an attack on a member country."
Nato condemned Syria after it shot down a Turkish warplane in June, without threatening any military action.
"We are not seeing red," Anatolia quoted Mr Arinc as saying. "But it is undeniable that we will seek our rights to the end faced with the loss of lives and an attack on our land."
Turkey's foreign ministry convened an emergency meeting over the incident.
Mr Davutoglu briefed Lakhdar Brahimi, the United Nations and Arab League special envoy to Syria, about the matter, NTV said.
He also called Mr Ban and Nato Secretary-General Anders Fogh Rasmussen to discuss the incident.
Mr Ban urged Mr Davutoglu to keep open all channels of communication with Syrian authorities with a view to lessening tensions between the two countries.
British deputy prime minister Nick Clegg praised Turkey for its "measured response to the events on their border thus far."
Mr Clegg, who discussed the violence during talks in Ankara today with president Abdullah Gul and Mr Erdogan, said in a statement that the UK "will continue to work with our partners in the region to manage the impact of the Syria crisis on security and stability."
Agencies