Pro-Kurdish political leaders accused Turkish President Tayyip Erdogan on Friday of trying to sow discord among Kurds ahead of a re-run of an Istanbul election on Sunday that is seen as a crucial test of support for Erdogan and his ruling AK Party.

The pro-Kurdish Peoples' Democratic Party (HDP) also reaffirmed its support for opposition mayoral candidate Ekrem Imamoglu.

In an unexpected and ambiguously worded statement, Kurdish militant leader Abdullah Ocalan called for "neutrality" in the Istanbul vote, in comments that could be understood as suggesting Kurds not take part.

Kurdish support was key in helping Imamoglu narrowly defeat the AKP mayoral candidate Binali Yildirim in the March vote. Kurdish voters account for about 15% of Istanbul's 10.5 million eligible voters and many support the HDP.

Just after state-run Anadolu agency released details of Ocalan's hand-written letter late on Thursday, Erdogan speculated in a television interview that the statement pointed to a "serious power struggle" among senior Kurdish leaders.

The HDP's co-leaders Pervin Buldan and Sezai Temelli responded angrily to Erdogan's intervention.

The effort by President Erdogan to set our party and Mr. Ocalan against each other through a text leaked in an unethical way shows ... how desperate he has become," they said."

There is no change in the HDP's election strategy and tactical steps," they said in a joint statement."