Damascus (AFP) - Prominent Syrian opposition activist Louay Hussein has evaded a travel ban and fled to Spain, days before he was due to face a verdict on charges of "weakening national sentiment".

"I arrived in Spain on Sunday after a difficult journey," Hussein, head of the Building the Syrian State party, told AFP by phone.

"I felt that my life was in danger."

Hussein was a leading member of the Syrian opposition inside the country, often referred to as the "tolerated" opposition.

The 55-year-old comes from the Alawite minority, the same Shiite sect to which President Bashar al-Assad belongs.

But he was arrested in November 2014 on charges of "weakening national sentiment", and placed under a travel ban when he was released on bail in February.

Hussein lambasted the regime after his departure.

"It's no longer possible to come to an understanding with the regime, which is turning into a militia," he told AFP.

Anas Judeh, deputy head of the Building the Syrian State party, said Hussein had flown from Damascus to the northeastern city of Qamishli.

"He then headed to the border town of Ras al-Ain, then into Turkey on his way to Spain," Judeh said.

Hussein had said he was visiting the northeast to learn more about the autonomous rule in the area in the absence of Syrian security forces.

"We did not know about his intention to leave. The news hit us like a bolt of lightning," Judeh told AFP.

Hussein said he would head to Istanbul in the coming days to meet members of the opposition, notably the internationally recognised National Coalition.

"I will go to Istanbul to meet with the leadership of the National Coalition and the transitional government, as well as other members of the opposition, so we can agree on a roadmap to save the country from the regime, the extremist Islamic State group, and the (Al-Qaeda affiliate) Al-Nusra Front," Hussein wrote on his personal Facebook page.