BEIRUT -- A series of airstrikes Friday in opposition areas in Syria's northern Aleppo province killed at least 18 people, including children and two hospital staffers, when the missiles hit an open market, a women and children's hospital and a village, activists and rescue workers said.

Airstrikes hit the only hospital for women and children in the town of Kafr Hamra before dawn Friday, killing two staffers including a nurse. The first-responders team of Syrian Civil Defense said it pulled 10 people alive from under the rubble.

Kafr Hamra is adjacent to the northern frontline in the deeply divided city of Aleppo, where government troops have sealed the main route into opposition areas, effectively trapping nearly 300,000 residents.

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The opposition fighters launched a counteroffensive last week, breaching the siege from the southern front. That road remains under fire, and the U.N. has asked for a cease-fire to allow aid into the area.

Health facilities have been frequently targeted in the civil war in Syria. Aid groups have said the month of July was one of the worst since the war began in 2011, with some 43 facilities in opposition areas partially or totally destroyed.

Despite calls for cease-fire and a promise from Russia of a three-hour respite to allow in humanitarian aid, there has been no let up in the violence.

During the day Friday, airstrikes hit a market area in the southwestern Aleppo Province town of Urem al-Kubra, killing at least six people, according to the Britain-based Syrian Observatory for Human Rights, which monitors the war in Syria. Urem al-Kubra lies on the road linking Aleppo to the northern rebel-controlled province of Idlib, which has also witnessed intense bombings.

In the northern Aleppo countryside, at least 10 people were killed, including children and women, when airstrikes hit the village of Hayan. It was not clear what the target was but videos shared by activists of the scene of the attack shows bodies of women and children strewn on the side of the road as frantic locals scramble to pick them up.

Activist-operated Facebook page the Local Coordination Committees said collective open air Friday prayers were called off in Idlib because of the intensity of the airstrikes. Muslims around the world perform the weekly Friday prayers in and outside mosques.

Germany's foreign minister called for U.N.-supervised humanitarian access to Aleppo, saying a unilateral three-hour daily cease-fire isn't enough. A senior U.N. humanitarian official already has said that a 48-hour pause each week is needed in view of the logistics of providing aid.

German Foreign Minister Frank-Walter Steinmeier was quoted as telling Friday's edition of the daily Frankfurter Allgemeine Zeitung that "humanitarian access can't be under the single-handed control of one side of the conflict."

"A unilaterally declared three-hour cease-fire per day isn't enough to avoid a humanitarian catastrophe," he said.

The Russian military is fighting alongside Syrian government forces in the civil war.

The U.S., meanwhile, has backed some rebel factions -- purportedly "vetted" moderates, rather than the Islamic extremists of al Qaeda's affiliate or ISIS.

As CBS News correspondent Charlie D'Agata reported Wednesday, American special operations forces are known to be training rebels in neighboring Jordan, and this week video emerged appearing to show them with those fighters, approaching the ISIS stronghold of Bukamal, in Syria.

The troops are stopped short by a hail of gunfire and forced to retreat. Where the video came from is also troubling; it was released as an ISIS propaganda video, with English captions.

ISIS could have seized the video off rebel fighters. A more worrying theory, says CBS National Security Analyst Fran Townsend, is that it could be the work of an insider.

"Has ISIS been able to penetrate Syrian rebel forces and get inside one of these training camps? That poses a whole host of security concerns, because you run the risk that once they have access to the training sites, it's a counterintelligence problem as well as a security problem," Townsend said.

The New Syrian Army has been America's latest hope in fighting ISIS on the ground -- specializing in counter-terrorism, and given the weapons and equipment to do it.