Turkey has asked for permission to search Saudi Arabia's consulate for prominent Saudi journalist Jamal Khashoggi, who went missing last week, broadcaster NTV said on Monday.

Turkish officials told Reuters over the weekend that they believed Khashoggi had been killed inside the Saudi consulate in Istanbul, and President Tayyip Erdogan said he was personally following the case.

On Monday, a Turkish official also said Saudi Arabia's envoy to Ankara had been summoned to the foreign ministry for a second time on Sunday and had been asked by Turkish diplomats to be "in full coordination" on the matter.