It's time for the United States to hold Iran accountable.

Gunmen and suicide bombers on Wednesday launched twin assaults on Iran's parliament and the tomb of the country's revolutionary founder Ayatollah Ruhollah Khomeini in Tehran, leaving at least 12 people dead and scores of others injured.

The Islamic State group claimed responsibility for these attacks, marking the first time the Sunni extremists have taken responsibility for an assault in Shiite-majority Iran.

Assailants armed with Kalashnikov rifles stormed the parliament building. One of the attackers later blew himself up inside, where a session had been in progress, according to a statement carried by Iran's state TV.

Deputy Interior Minister Mohammad Hossein Zolfaghari told Iran's state TV the apparently male attackers wore women's attire.

Later, a news agency reported that the siege had ended with four of the attackers killed.

Soon after the parliament attack, a suicide bomber and other assailants targeted the shrine of Ayatollah Ruhollah Khomeini located just outside the capital, Tehran, according to Iran's official state broadcaster. It said a security guard was killed and that one of the attackers was killed by security guards. A woman was also arrested.

Click here to read more.