KABUL, Afghanistan (CNN) -- Suspected militants ambushed a police checkpoint in southern Afghanistan on Thursday, killing nine officers, the interior ministry said.
The pre-dawn attack occurred in a district in Helmand province, the ministry said.
Officials blamed the attack on "the enemies of Afghanistan" -- a term the government regularly uses to describe the Taliban or foreign fighters inside the country.
Authorities launched an operation to track down the attackers.
Helmand province is an important front in the war against Islamic militants. The province is considered the world's largest opium poppy-growing region, and that trade has helped fund insurgent activities.
Journalist Aleem Agha contributed to this report.