The Latest on the conflict in Syria (all times local):

6:30 p.m.

The Russian Defense Ministry says the U.S. has dragged its feet on responding to Moscow's proposals on joint monitoring of a Syria cease-fire.

Lt. Gen. Sergei Kuralenko said Saturday that Russia proposed measures on controlling the truce on Feb. 25, but the U.S. hasn't answered yet, adding that further delays led to civilian casualties and were "inadmissible." Kuralenko said 67 civilians have been killed by militant fire in Aleppo alone since the truce started.

The Russian and U.S.-brokered cease-fire that began on Feb. 27 has helped significantly reduce hostilities. The Islamic State group and the al-Qaida-linked Nusra Front have been excluded from the truce.

President Vladimir Putin has recalled some Russian warplanes from Syria earlier this week, but said the air strikes against the IS and the Nusra Front will continue

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2:30 p.m.

Opposition monitoring groups say airstrikes have killed and wounded dozens of people in the northern Syrian city of Raqqa, the Islamic State group's de facto capital.

The Britain-based Syrian Observatory for Human Rights says 19 people were killed and some 60 wounded when the air raids hit several areas in the city, which has been held by the extremists since 2013.

The Local Coordination Committees said the air raids were carried out by Syrian government warplanes, adding that dozens were killed or wounded.

Both groups say Saturday's air raids struck near the national hospital, a former army base and other neighborhoods.

They say most of the casualties were civilians.