Iran has expelled four Azerbaijani diplomats a month after a similar move by Baku highlighted a deterioration of relations between the neighbors, the Iranian state news agency IRNA reported on Friday.
IRNA did not give further details of the action, which came after Azerbaijan said in April that it was expelling four Iranian diplomats over "provocative actions."
Tensions have been triggered in part by Baku's improving relations with Tehran's arch-enemy Israel. The dispute came to a head when Baku opened an embassy in Israel in late March.
During the row, Azerbaijan suggested that Iran may have been connected to an attempted assassination of an anti-Tehran Azerbaijani lawmaker. Tehran has denied the accusation.
Iran, which has a large population of ethnic Azeris in its northwest, has strongly criticized Azerbaijan for moving closer to Israel, with its foreign ministry saying it sees the relationship between Azerbaijan and Israel as "anti-Iranian."