Kabul, Afghanistan (CNN) -- An anti-insurgent provincial governor who had survived Taliban assassination attempts was among 20 people who died Friday in an explosion at a northern Afghan mosque during prayers, a government official said.

The blast in Afghanistan's Takhar province killed Kunduz provincial governor Mohammad Omar, who recently sounded an alarm about the threat of insurgents during an interview with CNN.

The bombing also wounded 35 others, with most of those killed and injured engaged in prayer, said Afghan Interior Ministry spokesman Zamarai Bashari.

"It is a terrible incident," said Bashari, who said police were trying to find out more details about the strike and who is responsible.

The NATO-led command condemned the attack, saying that "it's unconscionable that anyone would attack a mosque."

"It's clear the insurgents have no respect for the most holy of Islamic places," said U.S. Navy Rear Adm. Greg Smith, spokesman for NATO's International Security Assistance Force, or ISAF.

The U.S. Embassy in Kabul deplored the act, saying "whoever was responsible" for striking a house of worship "has demonstrated a clear lack of disregard for the Afghan people and for the peaceful religion they practice."

The mosque was bloodied and its roof was shattered, eyewitness Mujib Rahman said, but there were different early accounts on how the strike was carried out.

Gen. Daoud Daoud, commander of the Afghan Interior Ministry's northern zone, said a suicide attacker apparently sitting next to the governor detonated a bomb.

Faiz Mohammad Powhidi, a Takhar governor spokesman, told CNN that a pre-placed mine exploded. He explained that governor had been visiting his family and attending Friday prayers weekly in his native province of Takhar, which borders Kunduz.

Omar, who was a Pashtun, had survived several assassination attempts by the Taliban, and his brother was slain a few months ago.

He told CNN on Sunday that for the last two years, the security situation has deteriorated in Kunduz because insurgents decided to destabilize northern Afghanistan, which, until recently, had been relatively stable during the nine-year-old Afghan conflict.

The Takhar blast and the Thursday killing of a German soldier in the north illustrates a growing unrest that contrasts with the first years after the Taliban's collapse in 2001. In those days, the north was much more secure than the predominantly ethnic Pashtun south and east of the country.

Omar told CNN that the insurgents were trying to use Kunduz as a launchpad to destabilize northern Afghanistan and the wider Central Asian region and lamented the lack of police available to battle insurgents.

"Currently 40 percent of Kunduz province is under Taliban control," he said.

German Foreign Minister Guido Westerwelle conveyed his regrets to the Afghan government in a letter.

"Yesterday we suffered the death of a Bundeswehr soldier," he said. "Today the news reaches us of another attack in which the governor of Kunduz, Mohammad Omar, was killed. I wanted to express my condolences on the part of the federal government."

Other violence rippled across the country on Friday.

Three coalition soldiers in southern Afghanistan were killed: one in an insurgent attack and two others in improvised explosive device attacks. NATO does not give the nationalities of service members who are killed, but the British Defence Ministry said one of its soldiers was killed in Helmand province in the south Friday.

NATO-led forces killed five armed men in eastern Afghanistan's Khost province. The command is investigating allegations of civilian casualties in the latter incident, ISAF said.