Iran's official news agency says gunmen have killed 14 Iranian guards on the border with Pakistan.

IRNA says five guards were wounded in the attack Friday outside Saravan in a mountainous region in southeastern Iran used by drug traffickers.

Authorities are investigating whether the attack was carried out by drug smugglers or rebels.

Iran is a major transit route for drugs that originate in Afghanistan and is trafficked across Iranian territory, with much of it bound for Western countries.