Somali government troops clashed with a regional militia on Friday, residents said, in one of the most serious outbreaks of fighting yet over political rivalries that Washington says are slowing the war against al Qaeda-linked insurgents.

Tension spilled over on Thursday evening between the Somali National Army and the Ahlu Sunnah Wal Jama’a (ASWJ) militia, a group of moderate Sufi Muslims which has played a key role in the fight against the al Qaeda-linked al Shabaab insurgency.

Clashes began in Dhusamareb, administrative capital of central Somalia’s Galmudug state, and spread to Guriel town, 60 km (40 miles) away, on Friday, residents said.

A resident said government forces had attacked a house where prominent ASWJ leaders live, and the two sides were fighting with mortars and anti-aircraft guns in the city center.

“After 11 years of peace, Dhusamareb city today is hell,” Halima Farah, who told Reuters by phone that she and her four children were cowering inside their flimsy house. “We are holding our children’s hands but we have no way out.”

Al Shabaab has been fighting the internationally-recognized Somali government since 2008. The militants have also attacked American military bases as well as bars, hotels, a shopping mall and a university in Kenya and Uganda. Two years ago, an al Shabaab truck bomb in Mogadishu killed around 500 civilians.

Somali government troops, supported by a 21,000-strong African Union peacekeeping force, launched a limited offensive against al Shabaab last year. But a top American diplomat said progress had petered out with the internal rivalries.

“The operation has stalled,” Rodney Hunter, the U.S. political coordinator to the United Nations, told the Security Council this week. “It is imperative that federal government and federal member states’ security services focus on combating al-Shabaab, rather than engaging in armed conflict with each other to resolve political disputes.”

Competition for political control and international security funds lie at the heart of the conflict.

Some regional states accuse the government of meddling in local elections to entrench allies ahead of national elections scheduled for this year. They also want a larger slice of the hundreds of millions of dollars that foreign donors spend annually on Somali security forces.