ISTANBUL — A United Nations investigation team arrived in Turkey on Monday to start an inquiry into the killing of the Saudi dissident Jamal Khashoggi three months ago inside the Saudi Consulate in Istanbul.

Agnès Callamard, the United Nations special rapporteur on extrajudicial, summary or arbitrary killings, met with the Turkish foreign minister, Mevlut Cavusoglu, in Ankara at the beginning of the planned weeklong visit. The minister posted a photograph of the meeting on Twitter.

Ms. Callamard said the inquiry was her own initiative, independent of the United Nations or any government. Turkey, however, had repeatedly said that it was considering requesting a United Nations investigation into the killing, because of frustration at Saudi Arabia’s failure to cooperate on a joint inquiry.

The Saudi government has placed 11 officials linked to the killing on trial in the capital, Riyadh, but has refused to extradite to Turkey any of those suspected of being involved.