Russian Foreign Minister Sergey Lavrov said his country remained "determined to fight terrorism" after a meeting Tuesday in Moscow with his Turkish and Iranian counterparts.
Karlov's body arrived in Moscow late Tuesday. The ambassador was bestowed honors upon arrival in a ceremony attended by Lavrov, Turkish Foreign Minister Mevlut Cavusoglu and the widow of the deceased, according to Russia's Foreign Ministry.
Earlier Tuesday, Lavrov said the tragedy made the talks even more urgent, according to Russian state-run news agency Sputnik.
"This tragedy makes all of us more determined to fight terrorism," Lavrov was quoted as saying.
He hoped the talks would "create conditions for a more efficient delivery of humanitarian aid without making any concessions to terrorists," he said.
"It is necessary to establish all the circumstances of the organization and (the) execution of the terrorist act as soon as possible."
Cavusoglu said the attack was intended to "harm our relations and destroy all the achievements we have made together recently."
He welcomed the investigative team from Russia, saying the two countries would work together to "uncover who is behind this vile and treacherous terror attack."
"Turkey and Russia have recently proven what they can achieve when they cooperate, not only to their own people but to the whole world," he said.
"We will maintain this cooperation in Syria in order to reach a political resolution and also extend the cooperation to other areas."
He announced the street that houses the Russian Embassy in Ankara will be renamed in Karlov's honor.
Shooter's relatives taken in for questioning
On Monday night, Altintas, the police officer, fired several shots at Karlov
, shouting, "Allahu akbar (God is greatest). Do not forget Aleppo! Do not forget Syria! Do not forget Aleppo! Do not forget Syria!"
Video and photographs taken during the exhibition show that shortly before the shooting, Altintas had been standing behind Karlov while the envoy was making remarks. Turkish security forces eventually killed Altintas, Turkey's Interior Ministry said.
Seven people were taken in for questioning in relation to the shooting, including the shooter's parents, sister, uncle and two other relatives. A roommate, a police officer, was also arrested, according to Turkish state news agency Anadolu.
Altintas' uncle was released under "judicial control," or bail-like conditions, Anadolu quoted security sources as saying.
According to Anadolu, the uncle was a former senior executive at a private school connected to cleric Fethullah Gulen
whose movement Turkey considers a terrorist group. The school was shut down after a failed coup in July.
Anadolu also reported that books about al Qaeda and Gulen's movement, which the Turkish government calls the Fethullah Gulen Terrorist Organization, were found after a search of Altintas' home.
Turkey alleges that members of Gulen's movement were behind the coup attempt.
The failed coup triggered a wave of arrests, detentions and dismissals of those suspected of any involvement.
The rest of Altintas' relatives were taken in for questioning, the agency quoted security sources as saying.
The ambassador's assassination came at a time of thawing relations between Russia and Turkey and at a pivotal moment in Syria in which Russia has been instrumental in President Bashar al-Assad's push to retake rebel-held areas.
Putin: Shooting a 'provocation'
Russian President Vladimir Putin said the killing was a clear provocation aimed at undermining not just the normalization of Russian-Turkish relations but also the "peace process in Syria" promoted by Russia, Turkey, Iran and other countries.
"The only response we should offer to this murder is stepping up our fight against terror, and the criminals will feel the heat," Putin said in televised remarks.
Turkish President Recep Tayyip Erdogan echoed Putin's sentiments, saying "the Russian government and the Turkish republic have the will to not fall into that provocation."
Putin will delay his annual news conference on Thursday in order to pay his respects to the slain ambassador, whose funeral will be held that day, Sputnik reported.
Roles of Russia and Turkey in Syria
Human rights groups and other countries have denounced Russia over its backing of the Syrian leader.
Moscow, the most powerful ally of the Assad regime, has carried out airstrikes since September 2015 to prop up the embattled ruler. As one of the five permanent members of the UN Security Council, Russia has used its veto powers to block a political solution to end the war.
The bombardment in Syria has drawn criticism from Western powers, with President Barack Obama on Friday accusing Russia of slaughtering civilians in the besieged city of Aleppo
in concert with the Assad regime. Moscow has recently tried to distance itself from the assault in eastern Aleppo.
Turkey's involvement in Syria is complicated. On one hand, the Turks are eager to help eradicate ISIS. On the other, Ankara has worked to drive Kurdish fighters from the Syrian side of the border.
Meanwhile, the United States supports Kurdish groups in both Syria and Iraq as critical partners in the battle against ISIS.
All US embassy and consulates in Turkey were to be closed Tuesday after a separate incident, hours after the Russian envoy's assassination.
Turkish police arrested a man who fired into the air with a shotgun outside the US Embassy in Ankara, Anadolu reported.
Video fed by Turkish video news agency IHA showed security officers leading a handcuffed man into an unmarked police car as he shouted in Turkish, "I swear to God. Don't play with us." No one was injured.