Oren Dorell

USA TODAY

Fighting escalated Thursday in the Syrian city of Aleppo, with an airstrike killing at least 27 people at a hospital supported by aid group Doctors Without Borders, according to a British-based monitoring group.

About 200 people have died in Syria during the past week of fighting, the Syrian Observatory for Human Rights said.

It wasn't immediately clear who was responsible for Thursday's strike on the hospital. Both the U.S. led coalition and Russia, which supports the regime of Syrian President Bashar Assad, denied they conducted airstrikes in the area.

At least 27 killed in airstrike on Syria hospital

White House press secretary Josh Earnest said the airstrike "fits the Assad regime's abhorrent pattern of striking first responders."

The attacks come two months after a partial cease-fire agreement to halt the Syrian civil war, but the increased fighting threatens to end hopes for a peaceful resolution of the five-year struggle.

Staffan de Mistura, the U.N. envoy for Syria, appealed Thursday to the United States and Russia to help revive the stalled peace talks in Geneva and the cease-fire, which he said "hangs by a thread."

The increased fighting is likely to produce bad consequences for Syria, its neighbors and U.S. allies in Europe. Here are five ugly outcomes.

Major attack looms

A sizable attack is possible by combined forces from Russia, Syria and Iran on opposition rebels in Aleppo. The United States expressed concerns last week about the massing of Syrian and Russian troops and equipment outside Aleppo.

Uptick in radical Islamist recruitment

Ongoing flow of refugees out of Syria increases pressure on U.S. allies in Jordan, Turkey and Europe. Such chaos creates good conditions for radical Islamist recruitment, said Syria analyst Chris Harmer at the Institute for the Study of War. The civil war has killed more than 270,000 people and displaced more than half the country's pre-war population of 22 million people.

Decrease in moderate rebel groups

Moderate rebel groups in Syria dwindle, as fleeing refugees represent their greatest source of support in the country. Aleppo, Syria's second-largest city before the war, is the last big-city stronghold remaining under moderate opposition control. Other major cities are either controlled by the Syrian government led by Assad, al-Qaeda's Syrian affiliate known as the Nusra Front or the Islamic State. Rebel fighters in Aleppo are intermingled with Nusra fighters and resist U.S. encouragement to separate, U.S. State Department spokesman John Kirby said.

ISIL holding territory

Despite continued U.S. pledges and actions to degrade the Islamic State, also known as ISIL or ISIS, the group will continue to fight and hold territory where it can plan attacks elsewhere. President Obama announced this week he approved sending an additional 250 special forces to Syria help opposition forces battle the Islamic State. The U.S. military said a Syrian Arab coalition it has organized to fight the Islamic State and attack its headquarters in Raqqa is not ready for that mission. "Everyone wants to see ISIS out of Raqqa, but it’s not going to happen," Syria analyst Harmer said. "Who's going to get there?"

Increased fighting between Syria's Kurds and Turkey

If Syrian government troops move on Aleppo, Syria's semi-autonomous Kurds could seek more independence and territory along the border with Turkey, a NATO ally. The United States supports both the Syrian Arab rebels in their fight against the Assad regime and the Kurds, who have been successful in fighting the Islamic State. But Turkey considers the main Kurdish militia a threat because of its connection to a terrorist group in Turkey that seeks independence.