The presidential candidate for the professional-Kurdish HDP, Selahattin Demirtas, is campaigning from jail after being arrested in November 2016.
If his celebration exceeds the 10% vote threshold required to enter Turkey’s parliament, that would jeopardise Mr Erdogan’s possibilities of a majority.
Speaking in regards to the bloodshed on Thursday, HDP co-chief Pervin Buldan condemned the killings and delivered: “We see that some are trying to incite the people with provocations.”
Mr Erdogan’s spokesman Ibrahim Kalin condemned the “hideous attack” on Twitter.
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BBC Turkey Correspondent Mark Lowen reports that the violence on Thursday came after a video leaked on social media presupposed to show President Erdogan advocating the intimidation of Kurds to win extra votes.
The video shows the president telling birthday party officials that they need to take care of the HDP. He then tells them that they have got the voter lists of every neighbourhood, and should do what is necessary.
He provides that if AKP officers arrive at polling stations before the other parties, in his words, “it may end ahead of it even starts”.
Image copyright Reuters Image caption A Girl holds footage of Selahattin Demirtas, jailed presidential candidate for the pro-Kurdish Peoples’ Democratic Party (HDP)
The president’s supporters have argued that that is a legitimate marketing campaign solution to maintain the competition.
His critics say he is encouraging the intimidation – or worse – of Kurdish electorate.
“Amidst what may well be the closest election in lots of years, it’s an increasingly more grimy combat for every vote,” our correspondent studies.