Turkey returns fire after strike
Syrian rebel forces are riven by divisions but Syrian government forces appear to lack the numbers to land a knockout blow and permanently hold rebellious areas.
US president Barack Obama on September 25th accused Iran of helping keep Dr Assad in power but has refused to arm Syria's rebels, partly for fear some of those fighting Dr Assad's rule are Islamist radicals equally hostile to the West.
Iran today called for the immediate release of Iranians held captive by Syrian rebels and said it would hold the rebels and their supporters responsible for their lives.
Syrian rebels seized a busload of 48 Iranians in early August on suspicion of being military personnel. Tehran says they were pilgrims visiting a Shia shrine in Damascus.
At least three rounds fired from Syria landed inside Turkey's Yayladagi district today, the office of the governor of the Turkish province of Hatay said.
It said the fire appeared to have been aimed by Syrian forces at rebels along the border.
There were no casualties.
Turkish border troops fired back mortars in response.
There were two similar incidents in Hatay yesterday, when Mr Erdogan issued his warning.
"Those who attempt to test Turkey's deterrence, its decisiveness, its capacity, I say here they are making a fatal mistake," he said in a bellicose speech to a crowd in Istanbul.
"We are not interested in war, but we're not far from war either. This nation has come to where it is today having gone through intercontinental wars," he said.
Turkish artillery bombarded Syrian military targets on Wednesday and Thursday, killing several Syrian soldiers after Syria's initial fatal bombardment.
The UN security council condemned the original Syrian attack.
Russia, a staunch ally of Syria, said it received assurances from Damascus the strike on Turkey was an accident but Mr Erdogan dismissed them, saying Syrian fire had repeatedly hit Turkey.
Wednesday's Syrian strike on the town of Akcakale was of a different magnitude to previous incidents, a Turkish official told Reuters.
"Wednesday was different. There were five or six rounds into the same place. That's why we responded a couple of times, to warn and deter. To tell the (Syrian) military to leave. We think they've got the message and have pulled back from the area."
Syria has since ordered its warplanes and helicopters not to go within 10km of the Turkish border and artillery units not to fire shells close to the border, according to Turkish broadcaster NTV.
Syria has not confirmed this.
Turkey's state-run Anatolian news agency said a large number of Turkish troops had been sent to the Oncupinar border area of Kilis province.