Thousands of people took to the streets in cities across Yemen Friday, calling for President Ali Abdullah Saleh to be put on trial. Saleh signed an accord on Wednesday to surrender power after 33 years of rule. Western countries and Yemen's neighbors fear the political instability could be exploited by terror groups.

Thousands of people took to the streets of the Yemeni capital after Friday prayers - protesting against the immunity from prosecution granted to President Ali Abdullah Saleh in return for his resignation.

"Our objection to the deal is the immunity from prosecution, which the Gulf Cooperation Council gave to him [Ali Saleh]," said one demonstrator. "This is the thing that we reject completely and that is why we wills stay here [protesting] until it is achieved."

There were simultaneous protests in Sana'a in support of the president. Local media say fighting broke out between security forces and army defectors.

Saleh signed the accord Wednesday, pledging to step down within 30 days and hand over power to his deputy before negotiations with the opposition. The deal was hailed as a breakthrough by its brokers, members of the Gulf Cooperation Council.

But Gala Riani of IHS Global Insight says many questions hang over the agreement.

"One of the problems is of course that Saleh remains, in name, as the president. Yesterday, five people were killed in Sana'a in clashes," said Riani. "Immediately afterwards you had a statement from ‘the President, Saleh', condemning what had happened and saying he would issue a probe into it. So that really poses an important question as to, ‘What kind of power does he still have?'"

Thousands of protestors watched the signing on television - which prompted celebrations in the capital. But Riani says many powerful institutions remain loyal to Saleh.

"Will he still be using these groups, including his son who is head of the Republican Guard, to interfere essentially in political affairs," asked Riani.

The West is paying close attention to what happens in Yemen. The man accused of trying to blow-up this Northwest Airlines Flight to Detroit on Christmas Day two years ago, Umar Farouk Abdulmutallab, is thought to have trained in the country.

The United States regularly conducts unmanned drone strikes against al-Qaeda targets in Yemen. in September a strike killed Anwar Al-Awlaki, accused by the U.S. of being the terror group's chief propagandist. Again, analyst Gala Riani:

"Even the U.S. I think is not keen to engage more with Yemen," she said. "What they want in Yemen is a political leadership that they can collaborate with. They certainly had that under Saleh. And they will be looking to perpetuate that and find another leadership that's willing to collaborate with them and willing to allow them to continue with their counter-terrorist operations."

Riani warns terror groups like al-Qaeda in the Arabian Penisula are seeking to exploit the political divisions in Yemen to gain more support on the ground.