President Raimonds Vejonis led the way, condemning what he called an "outrageous terror attack".
I strongly condemn outrageous terror attack in #Barcelona. My deepest sympathy to relatives and friends of victims.— Valsts prezidents (@Rigas_pils) August 17, 2017
Prime Minister Maris Kucinskis followed suit.
The Latvian Foreign Ministry said there were no immediate indications that Latvian residents had been caught up in the incident but urged Latvians in Barcelona to let friends and family know they were okay.
"The Foreign Ministry of Latvia currently has received no information about any casualties among Latvian nationals (citizens and non-citizens). Neither have any Latvian nationals been registered with the Consular Register," said a statement from the ministry.
"The Foreign Ministry and the Latvian Embassy in Spain are in contact with local law enforcement and rescue authorities concerning the identities of those who have suffered as the result of the incident," it added.
A special telephone hotline for consular assistance has been set up in both Spain and Latvia. Members of the public can also contact the ministry using the email address:[email protected]
Ja nepieciešama konsulārā palīdzība, zvaniet LV vēstniecībai Spānijā: +34 91 369 13 62 vai konsulārajam dežurantam Rīgā: +371 26 33 77 11— Ārlietu ministrija (@Arlietas) August 17, 2017
Defense Minister Raimonds Bergmanis said the Spanish and Latvian flags at Adazi military base were being flown at half-mast as a mark of respect.
Šodien Ādažu bāzē, kur atrodas arī spāņu karavīri, Spānijas un Latvijas karogi pusmastā. Esam kopā ar Spāniju, pieminot traģēdijas upurus! pic.twitter.com/ALJYAJOssI— Raimonds Bergmanis (@RaimondsBrg) August 18, 2017
The Spanish embassy in Latvia observed a minute's silence.