The leader of Turkey's ultranationalist Victory Party has backed the opposition candidate Kemal Kilicdaroglu defying the party's former presidential candidate Sinan Oan, who backed Recep Tayyip Erdogan.

At a joint news appearance with Kilicdaroglu, Victory Party chairman Umit Ozdag stated that the two had signed a memorandum of cooperation, which included commitments to deport all refugees in Turkey within a year of taking office.

They also agreed not to reinstate democratically-elected Kurdish mayors in Turkey's south-east who had been replaced with appointees as part of a state crackdown on the leftwing and predominantly Kurdish People's Democratic Party (HDP) - a jab at the Kurdish support that propelled Kilicdaroglu to victory in the first round.

“We reached a consensus with him. As the Victory party, we decided to support Kilicdaroglu in the second round,” he said.

Simultaneously, the HDP, whose jailed leader Selahattin Demirtas previously backed Kilicdaroglu, said it would meet to agree on how to respond.

The divided support comes only four days before Erdogan and Kilicdaroglu face a runoff in the presidential elections on May 28. Erdogan received little over 49.5% of the vote in the first round ahead of Kilicdaroglu at 44.5%.

Ogan, who campaigned on a clearly anti-refugee platform, received little more than 5% of the vote in the first round and expressed his support for Erdogan earlier this week.

“We believe that our decision will be the right decision for our country and nation,” he said. “I declare that we will support Recep Tayyip Erdogan, the candidate of the People’s Alliance, in the second round of the elections.”

The Victory Party had endorsed Ogan but said at the time that Ogan’s statement did not mirror the views of the party.

After the first round of voting, in which both he and Erdogan worked to recruit Victory Party voters to their side for the runoff, Kilicdaroglu has already doubled down on his own anti-refugee rhetoric.

The topic of Syrian refugees has been highly debated within Turkish politics, and its importance was highlighted in this year's presidential election campaigns, especially that of opposition leader Kemal Kilicdaruglo who said that if he emerges victorious, he intends to "say goodbye" to the refugees within two years.

On the other hand, Erdogan's government has mobilized on diplomatic levels to expand relations with Syria under Russian- and Iranian-mediated talks.