More than 40 people were reported killed in fighting in a key city in northern Iraq and gunmen took over a town elsewhere in the country Thursday, raising concerns that unrest roiling Sunni areas is spreading. Iraq’s prime minister appealed for calm following three days of violence that has left more than 150 dead.

Clashes erupted late Wednesday in Mosul between gunmen and police in some districts before security forces brought the situation under control before midday Thursday. Police said 31 militants and 10 police officers were killed in the fighting.

Meanwhile, the Defense Ministry said gunmen had taken control of the police station and other government buildings in Suleiman Beg, 90 miles north of Baghdad, and were deployed in the streets there. It did not provide information on casualties.

On Wednesday, police and hospital officials reported fierce clashes in the town that resulted in the deaths of four soldiers and 12 others, including some gunmen. The mayor of the city of Tuz Khormato, to which Suleiman Beg is administratively annexed, said security forces had laid siege to the small town and sporadic clashes were continuing.

The latest unrest began Tuesday when fighting broke out in the northern town of Hawija during a security crackdown on a protest encampment. Three members of the Iraqi security force and at least 20 other people were killed.

In his first public comments since the Hawija killings, Prime Minister Nouri al-Maliki urged Iraqis to unite against extremists.

“We all have to shoulder responsibility after what happened in Hawija and what’s going on today in Suleiman Beg and other areas,” he said in a televised address. “If [sectarian] conflict erupts, there will be no winner or loser. All will lose, whether in southern or northern or western or eastern Iraq.”

Northeast of Baghdad, the Iraqi army surrounded the town of Qara Tappah, where deadly clashes also were reported Wednesday. Gunmen also opened fire on a police checkpoint near Fallujah on Thursday, killing two policemen, according to police.

The turmoil is aggravating an already tense political situation between Sunnis and the Shiite-led government. On Thursday, a Sunni politician who recently resigned from the cabinet urged Maliki, a Shiite, to step down.

“Iraq is in a dire situation now, and I believe that there must be serious solutions,” former science and technology minister Abdul-Karim al-Sammarraie said in a phone interview.

— Associated Press