TEHRAN, Iran—Iran's state news agency says authorities have detained the son of influential ex-president Akbar Hashemi Rafsanjani two days after arresting the politician's daughter.

The IRNA report says authorities picked up Mahdi Hashemi on Monday, a day after he returned to Iran from Britain.

Hashemi sought refuge in Britain after Iranian authorities accused him of fomenting unrest in the aftermath of Iran's disputed 2009 presidential election. He also faced corruption charges.

On Saturday, Iranian authorities took Hashemi's sister, Faezeh, into custody to serve a six-month sentence on charges of making propaganda against the ruling system.

Since President Mahmoud Ahmadinejad's disputed 2009 reelection, in which Rafsanjani supported Ahmadinejad's reformist challenger, Rafsanjani's family has come under pressure from government hardliners.