Six senior Turkish politicians from the country's opposition Nationalist Action Party (MHP) have resigned from parliament over a sex video scandal.
Turkish media say the six, including four vice-presidents, quit following threats to publish compromising videos.
Four other senior MHP leaders resigned earlier this month after secretly filmed images were posted online.
The scandal has fanned tensions ahead of the June poll in which the Islamist-rooted AKP is seeking a third term.
Lawmaker Deniz Bolukbasi, one of the six MHP leaders who resigned on Saturday, said he had been the victim of a trap sponsored by Prime Minister Recep Tayyip Erdogan's AKP.
"I am resigning to spare my party the damage such allegations might cause," he was quoted as saying by the Associated Press news agency.
'Ugly plot'
The MHP, a nationalist group, is Turkey's second-largest opposition party.
The BBC's Jonathan Head in Istanbul says its performance matters a great deal, because Turkey has a high threshold for winning seats in parliament. If the MHP gets less than 10% support it will have no seats at all.
This, our correspondent says, would give the AKP a chance to achieve a 66% majority, which would allow it to fulfil its pledge to rewrite the constitution without holding a referendum.
An obscure group calling itself "Different Nationalists" has demanded that the entire MHP leadership step down, and earlier this month published the sex videos on the internet.
"The dark forces behind this ugly political plot, both at home and abroad, will come to light as part of the ongoing investigation," Mr Bolukbasi told AFP news agency.
Last year Deniz Baykal, the head of the main opposition party, the secularist Republican People's Party, resigned over a similar scandal after bedroom images of him and a female MP were posted on the internet.
Prosecutors have failed so far to find out who filmed and posted that video.
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