People held a photograph of jailed PKK leader Abdullah Öcalan in Diyarbakir, Turkey. AP
DEM, Turkey's third biggest party, has played a key role in facilitating contacts between the government and Ocalan, who has been serving a life sentence in solitary confinement since 1999.
In February, Ocalan urged the PKK to end its armed struggle for a Kurdish homeland and disband, which the group formally did in May, drawing a line under a decades-long conflict that has claimed more than 40,000 lives.
Lawmakers Pervin Buldan and Mithat Sancar travelled with lawyer Ozgur Faik Erol to Imrali prison island near Istanbul to see Ocalan, a DEM statement said.
After the visit, DEM said Buldan and Sancar would hold talks with President Recep Tayyip Erdogan at 1200 GMT on Monday at the presidential palace.
The talks came ahead of a planned ceremony by PKK militants in Iraqi Kurdistan to start destroying a first tranche of weapons -- due on or around 10-12 July.
Erdogan on Saturday said the move would give momentum to peace efforts with the Kurds.
The disarmament process is expected to unfold over the coming months.
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