Baku is demanding an explanation for the arrest of two Azerbaijani citizens in Iran.
Azerbaijan's Foreign Ministry said its consulate in the Iranian city of Tabriz handed a note of protest to the Iranian officials on May 2.
Iranian authorities confirmed on May 2 that Azerbaijani scientist Halida Halid and her assistant were arrested in Tabriz on April 30, along with four Iranian activists of Azerbaijani origin.
Last year, two Azerbaijani citizens, poets Shahryar Hajizadeh and Farid Husseinov, were arrested in Tabriz and held in Iranian custody for several months for allegedly promoting separatism in the Iranian province of East Azerbaijan.
Azerbaijan arrested 22 people last year and accused them of spying for Iran.