A suspected Islamic State suicide bomber killed at least 30 people, mostly young students, in an attack on a Turkish town near the Syrian border on July 20. Bodies lay beneath trees after the blast outside a cultural centre in the mostly Kurdish town of Suruc in southeastern Turkey, some 10 km (6 miles) from the Syrian town of Kobani, where Kurdish fighters have been battling Islamic State. The explosion tore through a group of mostly university-aged students from an activist group as they gathered to make a statement to the local press about a trip they were planning to help rebuild Kobani. Turkey's NATO allies have been seeking tighter controls on a porous border with Syria that runs alongside Islamic State-held territories. But monitoring is difficult with 1.8 million Syrian refugees now on the Turkish side and smuggling rife.

"Terror has no religion"

The Suruc attack comes weeks after Turkey deployed additional troops and equipment along parts of its border with Syria, concerned about the risk of spillover as fighting between Kurdish forces, rebel groups, Syrian government troops and Islamic State militants intensifies.

An explosion also occurred in Kobani shortly afterwards, which a monitoring group blamed on a car bomb. A spokesman for Syrian Kurdish forces, known as the YPG, said two fighters died.

Turkey's leaders have said they do not plan any unilateral military incursion into Syria but have also said they will do whatever is necessary to defend the country's borders.

"Terror has no religion, no country, no race," President Tayyip Erdogan said of the bloodiest such attack in Turkey since at least 50 people were killed in the town of Reyhanli near the border in 2013.

Ankara fears any disorder in the border area could re-ignite an armed Kurdish rebellion by the Kurdistan Workers Party (PKK) in the south-east that has killed some 40,000 since 1984. It must also consider the danger of attacks in sprawling Western cities such as Istanbul where British and Jewish targets were bombed by al Qaeda in 2003 with the loss of 60 lives.

Turkey's Kurds have been enraged by what they see as the AKP party government's failure to do more to stop Islamic State. The PKK held Ankara responsible for the attack on July 20, saying it had "supported and cultivated" Islamic State against the Kurds.

Police in Istanbul fired tear gas and water cannon after a demonstration by several hundred pro-Kurdish protesters on the central Taksim Square turned violent. "Murderer Islamic State, collaborator Erdogan and AKP", ran one slogan.

A police helicopter hovered overhead.