Turkish President Abdullah Gul said on Monday the "worst-case scenarios" were now playing out in Syria and Turkey would to do everything necessary to protect itself, while its army fired back for a sixth day after a shell fired from Syria flew over the border.
Gul said the violence in Turkey's southern neighbour, where a revolt against President Bashar al-Assad has evolved into a civil war that threatens to draw in regional powers, could not go on indefinitely and Assad's fall was inevitable.
"The worst-case scenarios are taking place right now in Syria ... Our government is in constant consultation with the Turkish military. Whatever is needed is being done immediately as you see, and it will continue to be done," Gul said.
"There will be a change, a transition sooner or later ... It is a must for the international community to take effective action before Syria turns into a bigger wreck and further blood is shed, that is our main wish," he told reporters in Ankara.
Turkey's armed forces have bolstered their presence along the 900 km (560 mile) border with Syria in recent days and have been responding in kind to gunfire and shelling spilling across from the south, where Assad's forces have been battling rebels who control swathes of territory.
The exchanges with Turkey are the most serious cross-border violence in Syria's revolt against Assad, which began in March last year with peaceful protests for reform and has evolved into a civil war with sectarian overtones.
Fighting further inside Syria also intensified on Monday.
"They have occupied buildings that we were stationed in and we had to evacuate," a rebel fighter told Reuters by Skype.
Skirmishes on the Syrian side of the border have been intensifying and it is unclear who fired the shells that have crossed into Turkey.
Damascus has said it fired into Turkey accidentally, but has failed to live up to pledges made last week, after a Syrian shell killed five civilians in the Turkish town of Akcakale, to ensure no more ordnance flies across the border.
The mortar round landed 150-200 metres inside the Turkish district of Hacipasa at about 3 p.m. (1200 GMT), the official said.
Reports in August said Shara, a former foreign minister who was appointed vice president six years ago, had tried to defect to neighbouring Jordan, but Syrian state media subsequently said he had never considered leaving.
"The opposition is inclined to accept these names. Farouq al-Shara has the ability to understand the system of the last 20-30 years," Davutoglu told the state broadcaster TRT.
"Farouq al-Shara did not get involved in the recent incidents, the massacre, in a very wise and conscientious attitude. But perhaps there is nobody who knows the system better than al-Shara."