The Russian investigation team were due to visit the Contemporary Arts Center in central Ankara where Russian envoy Andrei Karlov was gunned down, as part of the joint probe with Turkish police.

Dramatic footage of the shooting showed Karlov stumble and crash to the ground on his back as off-duty Turkish riot police officer Mevlut Mert Altintas fired nine shots into the veteran diplomat.

Terrified onlookers cowered behind cocktail tables as Altintas brandished his automatic pistol and shouted "Allahu Akbar" ("God is greatest") and "Don't forget Aleppo." He was killed by police during a standoff shortly after the attack.

Working together

Turkish President Recep Tayyip Erdogan said in a speech on Tuesday that he and his Russian counterpart Vladimir Putin had agreed that a recent thawing of relations between the two countries would "not be hampered by this attack."

Turkey and Russia worked together over the past two weeks to broker a ceasefire in Syria's war-ravaged city of Aleppo that has allowed tens of thousands of residents to leave opposition-held areas of the city.

The nearly six-year war in Syria has strained relations, as Moscow and Ankara back opposing sides.

On Tuesday, Putin ordered security at diplomatic missions at home and abroad to be stepped up as Karlov's remains returned home to Moscow. His coffin, draped in a Russian flag, was given a full Turkish state honors on the tarmac of Ankara's Esenboga Airport.

Several arrests

Six people have been detained over the assassination, including Altintas' sister, mother, father and uncle, Turkish media said.

One senior Turkish security official said investigators were focusing on whether Altintas had links to the US-based Muslim cleric Fethullah Gulen, whom Ankara blames for a failed July coup.

Police said Altintas called in sick to his police job on Monday and stayed at a hotel to prepare for the shooting. On arrival at the arts center, he avoided a metal detector security check, and although he was stopped by security, was allowed to proceed after showing his police ID.

mm/rc (AFP, dpa, Reuters)