Iran's official news agency says the country's constitutional watchdog has ratified results of the country's parliamentary elections.

IRNA says the Guardian Council on Wednesday approved election results of 207 constituencies, including Tehran, where a reformist-moderate bloc won all 30 seats of the city in the house.

In February, reformists and moderate allies of President Hassan Rouhani won the majority in voting for the 290-member assembly and a clerical body charged with choosing the country's next supreme leader.

Iran is to hold runoff elections for nearly a quarter of the seats in parliament on April 29.

The results were seen as a major setback for hard-liners opposed to the landmark nuclear deal reached with world powers last year, which lifted international sanctions in exchange for Iran curbing its nuclear activities.