Syrian shell kills five in Turkish town Tensions between Turkey and Syria reached a new high yesterday, as Ankara warned that it would not let a deadly shell attack go unanswered. A woman and four children were killed when a shell fired from Syria hit the border town of Akcakale, the first time Turkish citizens have died in cross border fire since fighting in Syria began last year. The news came amid a surge of violence in the Syrian city of Aleppo, with dozens killed as bombs tore through a main square, and follows more than a year of steadily worsening relations between the two former allies. "This last incident is the straw that broke the camel's back," said Bulent Arinc, a Turkish deputy prime minister. We will respond according to international law. In a sign that Turkey was looking to take the issue to both the United Nations and Nato, Ahmet Davutoglu, Turkish foreign minister, immediately briefed both Ban Ki-moon, UN secretary general, and Anders Fogh Rasmussen, Nato chief. Fierce fighting has been taking place on the Syrian side of the border with Akcakale, with regime forces attacking rebel-held territory. Six shells have fallen on the town this month so far and schools in the district have been closed due to fears about flying bullets. "We have been very nervous for the past ten days; every day we have been asking whether it is going to hit us today." said Abdulhakim Ayhan, Akcakale mayor, adding that there could still be people underneath the ruins. The incident was the gravest to date between the two former allies. In April, Syrian fire into a camp killed two Syrian refugees at a camp just acrross the border. In June Syrian forces shot down a Turkish jet that had briefly crossed over to Syrian airspace, killing two pilots. On that occasion, Recep Tayyip Erdogan, Turkish prime minister, who has become one of the fiercest critics of president Bashar al-Assad of Syria, announced that Ankara had changed its rules of engagement and that Turkey would henceforth respond to any Syrian forces that threatened its border. But Mr Erdogan has also made clear that he is deeply reluctant to become involved in a bilateral confrontation with Damascus, which he has described as a "trap." Initial comments by officials highlighted that Turkey remains intensely wary of such an outcome. "This is all an attempt to draw Turkey into Syria," Besir Atalay, another Turkish deputy prime minister, said of the shelling. Commentators said that after such a series of bloody incidents, Ankara would have to tread a difficult line between escalating the crisis and looking impotent. "There will be a lot of pressure on Erdogan for at least a show of force," said Soli Ozel at Kadir Has university in Istanbul. But there may be a slippery slope towards getting physically involved in Syria. The Turkish government has been campaigning hard for a UN-backed buffer zone in Syria, but the US has been unwilling to push for a vote on the issue in the Security Council - a reluctance that has exasperated Ankara and which Turkish officials link to next month's US presidential elections. US officials argue that a buffer zone would require a no-fly zone to protect the civilian population and that Syria's air defence could be difficult to overcome. Meanwhile in Aleppo, Syrian state television said "terrorist" suicide bombers had set off three explosions in the Saadallah al-Jabri square, killing at least 33 people. The state news agency however said that there were only two bomb attacks in the square and one a few hundred metres away, according to Reuters. The UK-based Syrian Observatory for Human Rights, a pro-opposition monitoring group, said that there were four bombs, including one which exploded near the chamber of commerce. At least 48 people were killed and 90 injured in the four explosions, mostly regime forces on checkpoints and in a nearby officers" club, it said. An intelligence building was also mortared, the group said. The pro-government TV station al Ikhbariya broadcast footage which seemed to show huge damage from the blast, with at least one building reduced to rubble.