An independent candidate has been shot dead in Istanbul ahead of Turkey's general election on 22 July.
Tuncay Seyranlioglu's car was hit by gunfire on a highway as it was taking him away from a TV studio.
The businessman, who had assets in media and property, was standing to be an MP in Istanbul. Several suspects are said to have been held over the attack.
Meanwhile, Turkey's prime minister has said he will quit politics if his party fails to win a decisive majority.
"If we can't come to power alone, I'll leave politics," local television quoted Recep Tayyip Erdogan as saying.
The prime minister's AK Party wants to win a majority large enough to enable it to form a strong government without relying on coalition partners.
Elections have been called early in Turkey in an effort to break a deadlock over a package of constitutional reforms proposed by the current government.
Those reforms include a proposal for the country's president to be elected directly by the people, rather than by parliament.
This is perhaps the world's first popular vote prompted by an e-coup
BBC Europe editor Mark Mardell
Read Mark's thoughts in full
They were put forward by the governing AK Party, whose candidate for the presidency, Abdullah Gul, was repeatedly rejected by parliament. Lawmakers accused him of Islamist leanings.
Turkey's current president and its secularist establishment have vowed to resist what they regard as the Islamist agenda of the AK Party.
Meanwhile, Turkish troops have been killed in a clash with Kurdish gunmen.
The soldiers were killed by suspected rebels from the Kurdistan Workers' Party (PKK) as they patrolled a rugged area near the south-eastern border with Iraq and Syria.
Turkish troops have been massing along the border with Iraq amid a recent rise in attacks by the PKK.
Turkey accuses Kurdish separatists of staging attacks from inside Iraq.