Activists are calling on Facebook users to turn their profile pictures red to shed light on the violence in Syria that has claimed the lives of hundreds of thousands of people. The call comes as a second medical facility was hit this week by airstrikes in Aleppo and at least 200 people have been killed in renewed fighting in the ravaged city. Many in the city are reportedly bracing for the possibility of a siege by the Syrian regime.

“‪#‎MakeFacebookRed to highlight the bloodshed in Syria especially in Aleppo where hospitals continue to be bombed and civilians killed on a daily basis,” one Facebook user wrote. “#MakeFacebookRed to raise awareness of the humanitarian catastrophe in Syria. ‪#‎AleppoIsBurning”

Aleppo was once the financial capital of Syria, but it has been gripped by fighting since the country spiraled into war five years ago. Few doctors remain in the city today and much of the population has fled. About half of Syria's population of 22 million has been displaced. Various factions have competed for control in the country's largest city as the Bashar Assad government has struggled to maintain its grip.

The attacks on medical facilities Wednesday and Friday are believed to have been carried out by the Syrian government. Human rights groups have charged the Assad regime with intentionally targeting hospitals in opposition-held areas.

Facebook users have frequently showed solidarity with victims following atrocities by changing their profile pictures, particularly after violence in Paris last November claimed 130 lives. As thousands changed their images to include the colors of the French flag, some questioned a purported double standard in ignoring violence elsewhere, particularly in Syria, Lebanon and Iraq at the time.

The latest bloodshed in Syria marks the apparent weakening of a ceasefire that many hoped would lead to a longer truce and, ultimately, a peace agreement. The Syrian army announced a temporary truce in Damascus, the capital, and various other areas Friday, but not in Aleppo. The United Nations is calling for the ceasefire to be "saved from collapse."