Turkey's pro-Kurdish party decided Thursday to continue backing the main opposition leader despite his overtures to far-right parties in the runup to this weekend's historic presidential runoff.

Secular candidate Kemal Kilicdaroglu alarmed his leftist Kurdish supporters by starting to court staunchly nationalist voters after losing to President Recep Tayyip Erdogan in the first round on May 14.

Kilicdaroglu put together the opposition's best performance of Erdogan's two-decade era in what is widely seen as Turkey's most consequential election of its post-Ottoman era.

But the 74-year-old still enters Turkey's first runoff vote Sunday trailing the conservative incumbent by nearly five points.

The pro-Kurdish HDP party and its green allies -- the third-largest voting bloc in the new parliament -- expressed particular alarm when Kilicdaroglu joined forces with a fringe far-right group this week.

Kilicdaroglu also unsuccessfully courted the endorsement of Sinan Ogan -- an ultra-nationalist who finished a distant third in the presidential ballot and threw his support behind Erdogan on Monday.

Turkish media reported that some HDP members wanted to call for a boycott of the second round in protest at Kilicdaroglu's tactics.

But HDP co-leader Pervin Buldan told reporters that staying away from the polls would only help Erdogan secure another five-year term.

"Erdogan is not an option for us," Buldan said.

"On May 28, we will complete the work that we left unfinished on May 14. In the face of those who try to prevent this demand for change, we will definitely go to the polls."

- Nationalist surge -

Kilicdaroglu's more overtly nationalist tone contrasts sharply with the inclusive campaign he ran in the first round.

The former civil servant tried to focus on healing Turkey's social divisions and pledged to defend Kurdish interests.

The long-repressed group represents up to a fifth of Turkey's 85-million-strong population and plays an important role in particularly close elections.

They broadly backed Erdogan when he and his Islamic-rooted party lifted some of the social and linguistic restrictions imposed on Kurds by staunchly secular governments in the past century.

But they turned against him when Erdogan broke off peace talks with Kurdish insurgency leaders and unleashed a sweeping crackdown in the wake of a failed 2016 coup.

Right-wing and nationalist parties emerged as the big winners of this month's parallel parliamentary polls.

Kilicdaroglu began to pledge to fight "terrorism" -- a Turkish euphemism for Kurdish groups that have been waging a bloody fight for broader autonomy since the 1980s.

He has also promised to immediately expel millions of Syrian and other migrants that have settled in Turkey since Erdogan came to power in 2003.

Buldan bluntly criticised Kilicdaroglu's new approach.

"It is wrong to score political points off immigrants or refugees," Buldan said.

"We will not back down from our stance under any circumstances."

But she added that her main goal on Sunday was ending Erdogan's "one-man regime".

zak/fo/imm