Turkey called on Monday for the full truth surrounding the killing of Saudi journalist Jamal Khashoggi to be revealed, as Saudi Arabia's public prosecutor held talks in Istanbul.

Khashoggi's death at the Saudi consulate in Istanbul nearly four weeks ago has escalated into a crisis for the world's top oil exporter, which initially denied any knowledge of or role in his death.

Saudi public prosecutor Saud Al Mojeb arrived in Istanbul overnight, days after he contradicted weeks of Saudi statements by saying that Khashoggi's killing was premeditated. On Monday he met Istanbul's chief prosecutor.