(CNN) -- At least 26 civilians, mostly women and children, were killed in violence last week In Afghanistan's Helmand province, a UN relief organization says.
The UN Assistance Mission in Afghanistan (UNAMA) said it "expresses its grave concern" over the deaths.
Helmand, in southern Afghanistan, had 891 civilian deaths or injuries last year, the highest total in the country outside of Kabul, UNAMA said.
On Thursday and Friday, international military forces conducted airstrikes in the Sangin District, reportedly targeting anti-government elements. UNAMA said at least 18 civilians died and a NATO-led mission called Resolute Support has begun an investigation.
UNAMA also cited Saturday's Taliban suicide car bombing in Lashkar Gah, capital of Helmand province, that killed at least eight people and injured at least 19 others. Many of the casualties were child vendors.
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