Many people across the country marked the day by marching on the streets with Azerbaijani and Turkish flags and chanting the slogans "Karabakh is Azerbaijan."
The tricolor was adopted on Nov. 9, 1918 as the national flag of Azerbaijan Democratic Republic (ADR) which existed for 23 months from 1918 to 1920.
Present-day Azerbaijan is considered the successor of the ADR, which claimed to be the first secular and democratic Muslim-majority country.
"The flag once raised will never fall!" became the motto of the country's independence struggle in the 20th century. They were the words of Mammad Amin Rasulzade, a statesman, prominent public figure and a founder of ADR.