A bombing in Najaf city, southern Iraq, that killed one person on Friday, was among a wave of violence in Iraq [EPA]
Sectarian tensions have escalated in Iraq, where the death toll from a four-day wave of violence has passed 190, officials have said.
Thousands of protesters gathered in cities across Iraq this week to voice their anger at the Shia-led government and called for Prime Minister Nouri al-Maliki to step down and an end to the discrimination against Sunnis.
A United Nations envoy, Martin Kobler, warned on Friday Iraq was at "crossroads" and called for restraint as violence continues to raise fears of a wider sectarian war.
The comments came as bombings at four Sunni mosques in and around Baghdad killed four people and wounded 50 on Friday, according to an interior ministry official and medics.
The violence was the latest in a wave of violence that erupted on Tuesday when security forces moved in against anti-government protesters near the Sunni northern town of Hawijah. The ensuing clashes left 53 people dead.
Sunni gunmen were also battling government forces on Friday after they took over Suleiman Beg, a town in Salahuddin province north of Baghdad, in response to a deadly raid in the town of Hawija on Wednesday.
Al Jazeera's Omar Al Saleh, reporting from Baghdad, said on Friday there were conflicting reports as to whether the armed groups or government were in control of the town.
Ahmed Aziz, the town's municipal council deputy chief, said the gunmen had pulled out of Suleiman Beg under a deal worked out by tribal leaders and government officials.
The gunmen had swarmed into the predominantly Sunni Turkmen town on Wednesday after deadly clashes with security forces, who pulled back as residents fled.
Abdul Baban, a local official, said helicopter fire wounded six people on the roof of a house in Suleiman Beg early on Friday.
The gunmen's capture of the town came amid a surge of violence which began on Tuesday when security forces moved in against anti-government protesters near Hawijah.
"The situation is really escalating," Al Jazeera's Saleh said.
He said that community leaders had called on Sunni soldiers in the Iraq army to leave their posts if the government ordered them to attack Sunni areas.
"I've been covering this story for more than four months; this is the first time I've seen armed men protecting the protests," our correspondent said.
"I saw people with rocket-propelled grenades.I saw people carrying sniper rifles and, very interestingly, the speaker who was addressing the crowd asked them if they were willing to die, and everybody rose in anger and they were shouting 'Allah Akbar [God is great]'."
'Willing to die'
The protest-related violence is the deadliest so far linked to demonstrations that broke out in Sunni areas of the Shia-majority country more than four months ago.
Thousands of protesters have called for the resignation of Maliki, a Shia, and railed against authorities for allegedly targeting their community.
Abdulghafur al-Samarraie and Saleh al-Haidari, leading clerics who respectively head the Sunni and Shia religious endowments, held a joint news conference on Wednesday in which they warned against sectarian strife and called for top politicians to meet at a Baghdad mosque on Friday.
Maliki himself warned of a return to "sectarian civil war" in remarks broadcast on state television on Thursday.
The meeting at the Umm al-Qura mosque was scheduled for 5pm (1400 GMT) on Friday, but it was unclear who would attend.