Syrian security forces on Saturday opened fire on thousands of protesters demanding regime change, killing at least 30 people in a sign that President Bashar Assad is prepared to ride out a wave of rapidly escalating international outrage.

The UN said it is sending a team into Syria to investigate and the European Union is expected to place sanctions on Syrian officials next week, both significant blows to Assad, a British-educated, self-styled reformer who has tried to bring Syria back into the global mainstream over his 11 years in power.

In Washington, State Department spokesman Mark Toner said the US was pressing the Syrian government to cease “violence against innocent citizens who are simply demonstrating and trying to state their aspirations for a more democratic future.”

The bloodshed was the latest spasm in what has become a weekly cycle of mass protests followed by a swift and deadly crackdown.

But pressure was mounting on Assad, who insists the unrest is a foreign conspiracy carried out by “terrorist groups.”

More than 580 civilians and 100 soldiers have been killed since the revolt began, rights groups say.

“What it looks like here is a systematic attack on a civilian population, a political decision to shoot to kill unarmed demonstrators and that could very well be a crime against humanity,” Human Rights Watch counsel Reed Brody told News channel.

Assad, who inherited power from his father in 2000, is determined to crush the revolt that has now become the gravest challenge to his family’s 40-year dynasty.

He has tried a combination of brute force, intimidation and promises of reform to crush the unrest, but his attempts have failed so far.

Still, Syria is a highly unpredictable country, in part because of its sizable minority population, the loyalty of the military and the regime’s web of allegiances to powerful forces including Lebanon’s Hezbollah and Shiite powerhouse Iran.

Serious and prolonged unrest are likely to hurt the regime’s proxy in Lebanon, Hezbollah, and weaken Iran’s influence in the Arab world.

Even as protests were raging today, Syria’s prime minister announced the formation of a committee to study ways to combat corruption.

In the past, the overtures would have been seen as significant concessions.

But protesters were largely unmoved, inspired by the uprisings sweeping the Arab world and enraged at the mounting death toll in Syria.