Prominent Syrian opposition figures said Thursday that the resignation of Kofi Annan, as a UN- Arab League joint special envoy to Syria, means the failure of his peace initiative to bring the 17-month-old crisis in Syria to an end, saying Syria is heading towards an all-out civil war.

Luai Hussain, head of the oppositional Building Syria State, told Xinhua that the resignation would "negatively affect" the situation in Syria, attributing the resignation to the escalation of the armed conflict in Syria.

Hussain said the Syrian crisis is heading toward a wide-scale civil war.

For his side, Hasan Abdul-Azim, head of the National Coordination Body, said the resignation means the failure of Annan 's plan, which calls primarily to a cessation of violence from all parties in order to pave the way for a national dialogue as a prelude to a political transition.

The plan was faltered from the very beginning due to the non- stop violence that has recently dramatically escalated and developed into an all-out urban battles.

Meanwhile, Abdul-Azim told Xinhua that the reason behind the plan's failure is the violence from both the regime and the armed opposition.

He said that the violence is now the "master of the situation," adding that the Syrian people are subject to the killing and displacement.

Abdul-Azim has further said that "all hopes for political solutions have stopped," adding that the situation is veering toward a civil war.

"This would jeopardize the unity of the Syrian people, the national facilities and institutions as well as the sovereignty of the homeland."

On Thursday, Annan said he was disappointed over the lack of progress in the Syrian peace process and that he would step down after his current mandate expires on Aug. 31.

At a press conference held in Geneva, Annan, who took the job as special envoy for Syria about five months ago, said he had informed the UN and the Arab League earlier in the day his intention.

Meanwhile, UN Secretary-General Ban Ki-moon announced the resignation of Annan, saying he wanted to express his deepest gratitude to Annan for the "determined and courageous" efforts he had made.

Annan, a former UN chief, was appointed as the special envoy to Syria on Feb. 23.

The Syrian Foreign Ministry lamented Annan's resignation decision, blaming the faltering peace efforts on the armed groups and their western backers.

It, however, stressed that Syria will remain committed to fighting terrorism, in accordance to the Syrian and UN Security Council laws with the aim to protect the innocent Syrians and preserve the public and private properties.

The ministry reassured the leadership's compliance with the peace plan.

On ground, the battles have continued unabated Thursday between the western-backed rebels and the Syrian troops amid reports that the United States has approved supporting the armed rebels.

Moreover, the Syrian Foreign Ministry on Thursday accused Turkey of playing a major role in supporting terrorism in Syria, adding that the United States and France have also explicitly announced their support to the armed insurgent groups that are committing crimes against the Syrian people.