TEHRAN, Iran (AP) — A suicide bombing targeting a bus carrying personnel of Iran's elite paramilitary Revolutionary Guard force killed at least 20 people and wounded 20 in the country's southeast, state media reported.

There was no immediate claim of responsibility for the attack, which came on the day of a U.S.-led conference in Warsaw that included discussions on what America describes as Iran's malign influence across the wider Mideast.

The state-run IRNA news agency, citing what it described as an "informed source," reported the attack on the Guard in Iran's Sistan and Baluchistan province.

The province, which lies on a major opium trafficking route, has seen occasional clashes between Iranian forces and Baluch separatists, as well as drug traffickers.

The Guard is a major economic and military power in Iran, answerable only to the country's supreme leader, Ayatollah Ali Khamenei.

While Iran has been enmeshed in the wars engulfing Syria and neighboring Iraq, it largely has avoided the bloodshed plaguing the region. In 2009, more than 40 people, including six Guard commanders, were killed in a suicide attack by Sunni extremists in Sistan and Baluchistan province.

A coordinated June 7, 2017 Islamic State group assault on Parliament and the shrine of Ayatollah Ruhollah Khomeini, the leader of Iran's 1979 Islamic Revolution. At least 18 people were killed and more than 50 wounded.

And most recently, an attack on a military parade in September in Iran's oil-rich southwest killed over 20 and wounded over 60.

Gambrell reported from Dubai, United Arab Emirates.