Doctors struggle to save wounded children in Homs

(CNN) -- The shrapnel wound is in the toddler's left side. The boy needs "a proper hospital," the doctor says, not the makeshift clinic in the Syrian city of Homs where he's being treated.

"Even the children are not allowed to get there," he says. "Where is the Red Cross that was negotiating yesterday?"

Soon afterward, the 2-year-old dies of his wounds. The child's father -- whose head, right hand and left knee are bandaged as well -- swears to avenge his death as the sound of artillery echoes outside.

"My son, what did you do?" he wails. "Who did you hurt?"

Baby's heartbreaking death in Syria

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Cut off and under fire in Homs, Syria

The scene was captured in a video shot by opposition activists in Homs, where Syrian government troops are shelling opposition-held neighborhoods for a third week. Opposition activists inside the city say Tuesday's bombardment was the worst to date, and children are among those dying for lack of proper treatment.

Rebellious doctors set up underground medical network

The International Committee of the Red Cross has called for a daily two-hour cease-fire so it can distribute aid to hungry, frightened and wounded civilians.

Syria's official news agency said reports that food and medical care were scarce are "lies." But the international humanitarian group Doctors Without Borders says government troops have been targeting doctors and hospital workers who treat those wounded in the nearly year-old Syrian clampdown.

Opposition videographer killed

The group says the result has been the creation of an underground system of clinics, since the government controls the established hospitals.

In the northern province of Idlib, opposition activists are distributing locally made video tutorials on first aid, including lessons on how to sew up and bandage bullet wounds and carry the wounded to safety.

But the opposition says the volume of casualties, coupled with shortages of basic supplies and trained medics, means people are dying of wounds that they would ordinarily survive.

The United Nations says more than 5,000 people have been killed as the government of Syrian President Bashar al-Assad tries to crush a growing movement against his rule that emerged nearly a year ago.

Aid group calls for cease-fire to treat wounded

Syrian opposition groups put the figure at more than 7,000.

CNN cannot independently verify opposition or government reports of casualties because the government has severely limited access to the country by international journalists.

CNN's Ivan Watson contributed to this report.