The United States on Saturday accused Syria of creating a ‘humanitarian crisis’ with its fierce crackdown on protests and called on Damascus to allow access for medics.

The remarks came after Syrian forces backed by helicopters killed at least 25 protesters across the country, including in and around the northwest town of Jisr al-Shughur, where thousands have fled across the Turkish border.

"The Syrian government's offensive in northern Syria has created a humanitarian crisis," the White House said in a statement. "The United States calls upon the Syrian government to stop this violence, and to give the International Committee for the Red Cross (ICRC) immediate, unfettered access to this region," it added.

"If Syria's leaders fail to provide this access, they will once again be showing contempt for the dignity of the Syrian people."

Protesters had taken to the streets again on Friday after Jumma prayers to demand the fall of the regime as part of the three-month uprising against the Assad family's 40-year rule.

More than 1,200 civilians have been killed since the revolt erupted in mid-March, according to rights groups.

Washington has toughened its stance in recent days, telling Syrian President Bashar al-Assad that he should halt the violence and either preside over a peaceful political transition or "get out of the way."

US President Barack Obama's administration has, however, stopped short of demanding that Assad step down. The United States has also thrown its weight behind a UN Security Council resolution proposed by Britain and France that condemns Syria for its brutal crackdown on opposition protesters. But Russia, one of five veto-wielding members of the council, opposes any resolution on Syria