SURUC, Turkey (Reuters) - 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 Monday.

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.

The United States, which has an air base at Incirlik in southern Turkey, though it is not being used for its air attacks on IS forces, called the bombing a “heinous terror attack”.

Prime Minister Ahmet Davutoglu told a news conference in Ankara 30 people had been killed. “It is...most probably a suicide bombing.”

The Hurriyet newspaper said the attacker was an 18-year old woman, but there was no confirmation.

“Turkey has taken and will continue to take all necessary measures against the Islamic State,” Davutoglu said, without giving details. “Measures on our border with Syria...will be increased.”

One witness, giving his name as Mehmet, told Reuters by telephone he saw more than 20 bodies.

“It was a huge explosion, we all shook.”

Video footage showed young men and women standing behind a banner declaring support for Kobani, some holding up small red flags. Suddenly there was a huge explosion, apparently from within the crowd, sending up a column of flame.

“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.

The body of a victim, covered by newspapers, lies next to a coffin after an explosion in Suruc in the southeastern Sanliurfa province, Turkey, July 20, 2015. REUTERS/Ahmet Bulte/Ihlas News Agency

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 Monday’s attack, 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.

REBUILDING KOBANI

Kobani was the site of one of the biggest battles against Islamic State last year and was secured by Syrian Kurdish fighters last month after repeated assaults.

The YPG drove the Islamist militants back from the town with the help of U.S. air strikes after months of fighting and siege.

The students from the Federation of Socialist Youth Associations had been planning a trip to Kobani to build a library, plant a forest and build a playground, Fatma Edemen, a member of the group wounded in the blast, told Reuters.

“I was behind a banner so I couldn’t see the attacker, but we understand it was a suicide attack. I was thrown to the ground...I jumped up and began running before I even realised I was hurt,” Edemen, a 22-year-old journalism student at Ankara University, said by telephone.

The blast came after a series of attacks on the Kurdish HDP party in the run-up to a June 7 election in Turkey, including two small bombs at a political rally in the city of Diyarbakir, which the party blamed on Islamic State sympathisers.

“What gives us pause about this attack is that while the others were haphazard and sloppy ... the size of this explosion suggests something more sophisticated,” said Aaron Stein, an Atlantic Council fellow who specialises on Turkey and Syria.

“That would suggest organisation beyond a lone wolf cooking up something in their kitchen.”