Dozens of people were killed and over 140 wounded when gunmen opened fire with automatic weapons on concertgoers near Moscow on Friday, one of the deadliest attacks on Russia in decades.
Islamic State, the militant group which once claimed control over swathes of Iraq and Syria, claimed responsibility for the attack.
Here is some early reaction:
"The images are just horrible and just hard to watch and our thoughts obviously are going to be with the victims of this terrible, terrible shooting attack."
"The entire world community is obliged to condemn this monstrous crime. All efforts are being thrown at saving people."
"Let's be straight about this: Ukraine had absolutely nothing to do with these events.
"We have a full-scale, all-out war with the Russian regular army and with the Russian Federation as a country. And regardless of everything, everything will be decided on the battlefield."
YULIA NAVALNAYA, WIDOW OF RUSSIAN OPPOSITION LEADER ALEXEI NAVALNY
"All those involved in this crime must be found and brought to justice."
ITALIAN PRIME MINISTER GIORGIA MELONI
"The horror of the massacre of innocent civilians in Moscow is unacceptable. Firm and total condemnation of the Italian government for this heinous act of terrorism."
FRENCH FOREIGN MINISTRY
"The images coming out of Moscow are terrible. Our thoughts go out to the victims and injured and to the Russian people.
"Light must be shed on these odious acts."
GERMAN FOREIGN MINISTRY
"The images of the horrific attack on innocent people at Crocus City Hall near Moscow are horrific. The background must be clarified quickly. Our deepest condolences go out to the families of the victims."
VENEZUELAN FOREIGN MINISTER YVAN GIL
"We express our strongest condemnation of the armed attack that has been carried out against civilians today in Moscow in the exhibition center Crocus City Hall. We send out condolences to the families of the victims and we stand in solidarity with the Russian government."
US REPUBLICAN SENATOR MITT ROMNEY
"The intentional targeting and murder of civilians is vile and evil regardless of the perpetrators - Putin against Ukrainians and terrorists against the Russians. Today's massacre in Moscow is tragic."
