Foreign Ministry spokeswoman Mao Ning said on Tuesday that the red line of protecting civilians in armed conflicts must not be crossed, and indiscriminate use of force is unacceptable.

"We are deeply saddened by the significant civilian casualties caused by the conflict," Mao told a regular news briefing, as the United States and Israel continued to trade military strikes with Iran.

China calls on all parties to fulfill their obligations under international law, effectively ensure the safety of civilians and avoid attacking civilian facilities, she added.