Nato said it had drawn up plans to defend Turkey if necessary should the war in Syria spill over their border again as dozens of people were killed across the Arab nation on Tuesday.
Fighting between Syrian rebels and government forces could be heard from this Turkish border town following on from several days of clashes in the past week.
One Syrian villager said a rebel push on the town of Azmarin was expected soon.
In Damascus, rebel suicide bombers struck at an Air Force Intelligence compound used as an interrogation centre - the latest attack to bring the conflict close to president Bashar al-Assad's power base.
"Assad...is only able to stand up with crutches," Turkish prime minister Tayyip Erdogan told a meeting of his ruling AK Party.
"He will be finished when the crutches fall away."
Erdogan, reacting to six consecutive days when shells fired from Syrian soil have landed on Turkish territory, has warned Ankara will not shrink from war if forced to act.
But his government has also stressed it would be reluctant to mount any big operation on Syrian soil and then only with international support.
It was not clear whether the shells hitting Turkish territory were aimed to strike there or were due to Syrian troops overshooting as they attacked rebels to their north.
Nato secretary-general Anders Fogh Rasmussen said in Brussels the 28-member military alliance hoped a way could be found to stop tensions escalating on the border.
"We have all necessary plans in place to protect and defend Turkey if necessary," he said.
Elsewhere in Syria, rebels took control of the town of Maarat al-Nuaman, which lies on the main north-south highway in the northern province of Idlib, after a 48-hour battle with soldiers, according to rebels and activists.
Video sent to Reuters, which activists said was filmed in Maarat al-Nuaman on Monday, showed dozens of fighters on a main street.
Other footage purported to show fighters taking over a prison and army-held buildings in the town.
The British-based Syrian Observatory for Human Rights, which monitors the violence, said 90 people had been killed so far on Tuesday, including 29 soldiers, compared to a death toll of 210 on Monday.
Activists estimated more than 100 dead or wounded in the bombing of the intelligence compound in Damascus.
The militant Islamist group al-Nusra Front said it had mounted the attack because the base was used a centre for torture and repression.
"Big shockwaves shattered windows and destroyed shop facades. It felt as if a bomb exploded inside every house in the area," said one resident of the suburb of Harasta, where the compound was located.
The sharp rise in casualties in the past month indicates the growing intensity of the war, which developed from peaceful protests against Assad in March 2011 into a full-scale civil war.
An estimated 30,000 people have been killed as main cities such as Aleppo, Homs and the capital itself are savagely contested.
UN special envoy Lakhdar Brahimi will go to Syria soon to try to persuade the Assad government to call an immediate ceasefire.
ON THE BORDER
In the border area, there was no sign of any breakthrough by either side though activists said rebels killed at least 40 soldiers on Saturday in a 12-hour battle to take the village of Khirbet al-Joz.
Just outside Hacipasa, nestled among olive groves in Turkey's Hatay province, the sound of mortar fire could be heard every 10 to 15 minutes on Tuesday from around the Syrian town of Azmarin. A Syrian helicopter flew over the border.
Villagers used ropes and boats to ferry the wounded across a river into Turkey.
Rebels with AK-47s slung over their shoulders carried a Free Syrian Army officer down to the river bank on the Syrian side, using a carpet and two poles as a makeshift stretcher.
He had been shot in the chest and had a chest drain and drip attached.
The rebels said they had dealt with roughly 20 wounded people and two dead on Tuesday.
The seriously wounded are ferried across to Turkey, while those less severely hurt are patched up at a makeshift first aid centre on the river bank and sent back into Syria.
Musana Barakat, 46, an Azmarin resident who makes frequent trips between the two countries, pointed at plumes of smoke in the distance and said Assad's troops were burning houses there.
"There are rebels hiding in and around the town and they are going to make a push tonight to drive Assad's forces out," he said, a Syrian passport sticking out of his shirt pocket.
A crowd gathered around a saloon car, the blood-stained body of a man who had been pulled wounded from the fighting slumped across its back seat.
Those with him said he had been rescued alive but died after being brought over the border.
Turkish President Abdullah Gul said on Monday the "worst-case scenarios" were now playing out in Syria and Turkey would do everything necessary to protect itself.
Gul and Erdogan, in seeking Western and Arab support, have repeatedly warned of the dangers of fighting in Syria spilling over into a sectarian war engulfing the entire region.
Turkey's chief of general staff, General Necdet Ozel, flew by helicopter to several bases in Hatay province on Tuesday, part of Turkey's 900km border with Syria.
The shelling of the Turkish town of Akcakale last Wednesday, which killed five civilians, marked a sharp escalation.
Turkey has been responding in kind since then to gunfire or mortar bombs flying over the border and has bolstered its military presence along the frontier.
"We are living in constant fear. The mortar sounds have really picked up since this morning. The children are really frightened," said Hali Nacioglu, 43, a farmer from the village of Yolazikoy near Hacipasa.
Unlike the flat terrain around Akcakale, the border area in Hatay is marked by rolling hills with heavy vegetation.
Syrian towns and villages, including Azmarin, are clearly visible just a few kilometers away.
"It's only right that Turkey should respond if it gets fired on but we really don't want war to break out. We want this to finish as soon as possible," said Abidin Tunc, 49, a tobacco farmer also from Yolazikoy.
Turkey was once an ally of Assad but turned against him after his violent response to the uprising.
It has nearly 100,000 Syrian refugees in camps on its territory, has given sanctuary to rebel leaders and has led calls for Assad to quit.