By BASSEM MROUE
BEIRUT (AP) — The U.S. and its European allies called on Syrian President Bashar Assad to resign Thursday as activists reported more bloodshed overnight and a high-level U.N. human rights team said Assad's crackdown on dissent "may amount to crimes against humanity."

Assad is coming under mounting criticism for his assault on a 5-month-old uprising. Human rights groups and witnesses accuse Syrian troops of firing on largely unarmed protesters and say more than 1,800 civilians have been killed since mid-March.

On Wednesday, Assad told the United Nations chief that military operations in his country have ended — but the statement did not stop Thursday's wave of calls for him to leave.

In a stinging written statement, President Barack Obama said Assad has overseen a vicious onslaught of his people as they protest for freedom. It was Obama's first explicit call for Assad to step down.

Obama said Assad's calls for reform ring hollow while he is "imprisoning, torturing and slaughtering his own people."
The leaders of France, Britain and Germany issued a statement saying Assad should "leave power in the greater interests of Syria and the unity of his people."

In a report released in Geneva, a U.N. team said the violence in Syria should be referred to the International Criminal Court. Crimes against humanity are considered the most serious of all international human rights violations after genocide.
"The mission found a pattern of human rights violations that constitutes widespread or systematic attacks against the civilian population, which may amount to crimes against humanity," the U.N. investigators said in their 22-page report.

Much of Syria was quiet after sunrise Thursday, although activists reported intense shooting around noon in the flashpoint city of Latakia. On Wednesday, activists said security forces killed 18 people across the country.
Assad has unleashed tanks and ground troops in an attempt to retake control in rebellious areas. The military assault has escalated dramatically since the start of the holy month of Ramadan in August, killing hundreds and detaining thousands.

In New York, U.N. Secretary-General Ban Ki-moon spoke to Assad demanding the immediate end of all military operations and mass arrests, according to a statement issued late Wednesday by the U.N.
In response, Assad said that military and police operations had stopped, the statement said.

"We hope the news is true," said Syria-based rights activist Muhannad al-Hassani, who heads the Syrian Organization for Human Rights, when asked about Assad's comment. "The situation is still difficult."
Meanwhile, Switzerland recalled its ambassador to Syria, saying it wants to send a strong signal to Damascus to end the crackdown on anti-government protesters.

The Swiss Foreign Ministry said the decision was made "because Switzerland cannot tolerate the systematic human rights violations" by Syrian security forces against civilians.
It said the Swiss ambassador to Syria was being recalled for consultations but the action is not "a rupture of diplomatic relations" and the Swiss embassy in Damascus remains operational.

London-based Syrian Observatory for Human Rights said most areas of Syria were quiet Thursday except for shooting in the coastal city of Latakia's al-Ramel neighborhood. The city endured a four-day military assault starting Saturday that killed at least 37 people and forced thousands to flee their homes.

A Homs-based activist told The Associated Press that there was intense shooting all night until sunrise Thursday. In addition to the heavy machine gun fire, at least two explosions were heard, he said.
"We didn't sleep last night. The president said operations ended while about 20 people were killed yesterday," said the resident, speaking on condition of anonymity for fear of government reprisals. "Forces stormed neighborhoods and detained dozens."

The government insists its crackdown is aimed at rooting out terrorists fomenting unrest in the country. In comments carried on the state-run news agency Wednesday, Assad appeared to lash out at the international reproach, saying his country will not give up its "dignity and sovereignty."

With tension rising, the United Nations said it has temporarily withdrawn about two dozen "nonessential" international staff from Syria because of security concerns. U.N. deputy spokesman Farhan Haq said Wednesday that some family members of U.N. staff have been relocated to other countries.