BEIRUT — Army defectors ambushed dozens of Syrian troops and regime forces gunned down civilians during one of the bloodiest days of the 8-month-old uprising, which appeared Tuesday to be spiraling out of President Bashar Assad’s control.

Up to 90 people were killed in a gruesome wave of violence Monday, activists said. The extent of the bloodshed only came to light Tuesday, in part because corpses lying in the streets did not reach the morgue until daylight.

As the bloodshed spiked, Assad’s former allies were turning on him in rapid succession — a sign of profound impatience with a leader who has failed to stem months of unrest that could explode into a regional conflagration.

Turkey, Jordan and the 22-member Arab League all signaled they were fed up with Assad’s response to the uprising and were ready to pressure him to go.

Turkish Prime Minister Recep Tayyip Erdogan said Tuesday he no longer has confidence in the government led by Assad, a 46-year-old eye doctor who inherited power from his father 11 years ago.

“No regime can survive by killing or jailing,” said Erdogan, who cultivated close ties with Assad before the uprising began in March.

Turkey also canceled plans for oil exploration in Syria and threatened to cut electricity supplies to the country, which is burning through the $17 billion in foreign reserves the government had at the start of the uprising. Turkey provides around 7 percent of Syria’s total electricity consumption.

A day earlier, Jordan’s King Abdullah II said Assad should step down, the first Arab leader to publicly make such a call. And over the weekend, the 22-member Arab League took a near-unanimous vote to suspend Damascus from the regional body.

Although activists say the anti-government protesters have remained largely peaceful, an armed insurgency has developed in recent months targeting Assad’s military and security forces.

Thirty-four soldiers were killed Monday in an ambush in Daraa, the birthplace of the uprising, said Rami Abdul-Rahman, head of the British-based Syrian Observatory for Human Rights. The brazen attack by army defectors suggests a new confidence among troops who have sided with the protesters and highlights the potential for an armed confrontation to escalate.