More than 2,000 Jordanians braved blistering temperatures on Friday to demonstrate across the country against recent hikes in commodity prices, demanding sweeping political change and constitutional reform.

"Instead of raising prices, hold the corrupt accountable. Reform the constitution and let the people see the light," read one of the banners carried by around 1,000 protesters, including Islamists, leftists and youths, who marched in central Amman.

Syrian opposition leaders were meeting in Turkey on Friday in a bid to settle their differences and forge a united front to confront the escalating conflict in their homeland.

"We will work towards a unified vision," said Burhan Ghalioun, who stepped down last month as head of the main opposition group the Syrian National Council in the face of mounting splits that were undermining its credibility.

Syrian government forces have used sexual violence to torture men, women, girls and boys detained during the current conflict, Human Rights Watch said on Friday.

The New York-based group said it had interviewed 10 former detainees, including two women, who described being sexually abused or witnessing such abuse in detention.

The escalating bloodshed in Syria is hampering a hard-won U.N. observer force's ability to carry out its mission, its chief Major General Robert Mood said on Friday.

"The escalating violence is limiting our ability to observe, verify reports as well as assist in local dialogue and stability," the veteran Norwegian peacekeeper told reporters in Damascus.

Envoys from the Middle East Quartet met in Brussels on Friday amid calls from the Palestinians to step up action to halt continuing Israeli settlement activity.

Officials from the United States, United Nations, European Union and Russia gathered "to consult as they routinely do over the phone as well", said a spokesman for EU foreign policy Chief Catherine Ashton.

Russia on Friday denied holding discussions with other nations on a political transformation in Syria that would include the departure of President Bashar Assad.

"I read somewhere today that supposedly, U.S. State Department spokeswoman Victoria Nuland said something along the lines of the United States and Russia discussing a political transformation in Syria after the departure of Bashar Assad," Foreign Minister Sergei Lavrov told reporters.

Yemeni forces killed 15 al-Qaida fighters in a clash at a control station in Shabwa province on the country's only gas export pipeline, a military official and a witness said on Friday.

The clash took place during Thursday night when the militants attacked Station Nine on the pipeline in the eastern province, where the jihadist network remains active, the military official said.

Egypt's transition to democracy was thrown into further disarray on Friday after its top court ordered parliament dissolved and allowed a disputed candidate to remain in a divisive presidential runoff.

Activists and political figures have described the rulings as the final phase of a military coup that takes the transition back to square one.

Yemeni troops took control of the city of Shuqra on Friday after al-Qaida militants pulled out, the third jihadist bastion in the south to fall in the space of a week, a military official said.

"The army has taken control of Shuqra," said a military official, adding that "troops have taken positions in the center" of the coastal city while militants were seen fleeing.

Syrian authorities have uncovered an al-Qaida plot to bomb Damascus mosques around the main weekly prayers, state media reported on Friday.

A suspect detained on Thursday confessed that he had been planning a suicide bombing during Friday prayers at the al-Rifai Mosque in the heart of the capital, the official SANA news agency reported.