Efforts to resolve the political crisis in Yemen appear to be crumbling after the southern separatist party suspended its participation in talks to form a new government.

The so-called southern movement, that wants to break away from the North, has dubbed the talks an "absurd dialogue" and "a waste of time".

Only former President Ali Abdullah Saleh's General People's Congress party joined the three-day talks aimed at filling the power vacuum left after Yemeni President Abd-Rabbu Mansour Hadi and his cabinet resigned on January 22.

Adding to Yemen's turmoil, soldiers are threatening to block a major highway leading to the Bab el-Mandeb strait - a crucial shipping lane in the Red Sea.

The threat was made after Houthi fighters shot and killed an army commander and two of his guards in Al Hudaydah.

The first day of the meeting on Friday in Sanaa, the capital, was heavily secured by the Houthis, whom Saleh is accused of backing.

The growing influence of the Houthi movement has triggered protests in several cities under the slogan: "Revolt until the overthrow of the coup" forces, in reference to the militia.

They also demanded the release of scores of activists and journalists who have been rounded up by the Houthis since their overtake of Sanaa.

Hundreds of protesters rallied in the southern city of Aden to reject the solution offer of Houthi leader Abdel-Malek al-Houthi that includes forming a transitional presidential council formed of six members.

Uneven playing field

Three members would represent the north of Yemen and the other three would be from the south.

Al Jazeera's Jamal Elshayyal, reporting from Aden, said the southern movement pulled out of the talks because they saw the event as an "uneven playing field".

"They believe the Houthi movement ... is in control and so long as they hold the president and other figures under house arrest ... there's no point in these negotiations," Elshayyal said. 

Elsewhere in the country, witnesses said Houthis violently dispersed and detained demonstrators during nationwide rallies attended by tens of thousands.

Radwan Masoud, the head of a students' union at the universities of Sanaa and Amran, was reportedly among the detained.

Sanaa University has been the focal point of anti-Houthi protests, frequently dispersed by the rebels firing in the air and detaining activists.

Elshayyal said the street protests are significant because previous demonstrations against the Houthi takeover had previously been suppressed. 

"The fact that protests are taking place could be a sign that the fear barrier has been broken," he said. "This could be a card that the southerners can play: using popular power - not military [power] - for future negotiations."

In the central Baida province, protesters accused the UN envoy of failing to end Yemen's crisis.

Source: Al Jazeera and agencies