Police in Istanbul have detained 27 people for questioning about a deadly bomb attack on a bus carrying military personnel and their families in Turkey's largest city.
Tuesday's explosion left five people dead and 12 others wounded after a remote-controlled roadside bomb was detonated close to a military housing complex.
It was not clear whether the suspected perpetrators of the attack, which was claimed by a Kurdish group with links to the Kurdistan Workers' Party (PKK), were those arrested.
Besir Atalay, Turkey's interior minister, said: "We have achieved quite a bit of progress in the investigation. The incident is about to be thoroughly enlightened."
Those detained on Wednesday were rounded up in an operation by anti-terrorism police and special forces, the Anatolia news agency said.
Four soldiers and Buse Sariyag, a 17-year-old high school student who was travelling on the bus with her father, were killed in the attack.
Sariyag was laid to rest in Elmadag, a suburb of Ankara, on Wednesday.
"The martyrs are immortal, the motherland is indivisible," shouted a crowd of some 5,000 people, waving Turkish flags, as they marched to the cemetary after funeral prayers at a local mosque.
The Kurdistan Freedom Falcons, which is linked to the PKK, has claimed responsibility for the attack.
The deaths brought the number of soldiers killed in Turkey since Friday to 17.
A PKK commander threatened more attacks on Turkish targets on Wednesday, saying the Kurdish group would keep fighting until its demands for greater rights and autonomy are met, a pro-Kurdish news agency reported.
Firat News quoted Cemil Bayik, who is believed to be in northern Iraq, as saying: "It is not possible to end this struggle unless the Kurdish problem is solved ... It is not possible to repress the guerrillas' capacity for action.
"Our movement's ... strength to launch attacks will continue as long as the Kurdish people's demands for freedoms continue to exist."
Recep Tayyip Erdogan, Turkey's prime minister, demanded on Wednesday that European allies cut off funding for the PKK and extradite suspected fighters to Turkey.
|Tuesday's explosion left five people dead and 12 others wounded [AFP]
The bombing cast a shadow over a summit of 11 heads of state from southeast Europe in Istanbul, where Erdogan called for help in Turkey's 26-year fight against the PKK, which is labelled a terrorist group by the European Union and United States.
"European countries have not given Turkey the necessary support in its fight against terrorism," Erdogan told the summit.
"The financial support still hasn't been cut.
"There are countries that turn a blind eye to the organisation's activities and propaganda and do not return the criminals to Turkey."
Fighting has escalated in the southeast of Turkey, which is predominantly Kurdish, in recent weeks.
Turkish military forces have begun a major deployment along the border with Iraq.
It follows increased infiltration by PKK members into Turkey from the mountains of northern Iraq where thousands of the fighters are based.
The PKK has called off a year-old unilateral ceasefire and announced that it was resuming attacks on Turkish forces, saying Ankara has rejected calls for dialogue.
The group accuses the military of waging attacks and the government of impeding a political resolution of the conflict.
More than 40,000 people, mostly Kurds, have been killed in violence since the PKK launched its armed struggle against the Turkish state in 1984.