Activists on Tuesday accused Nigeria's military of killing hundreds upon hundreds, perhaps as many as 1,000, Shiite Muslims in just three days in what the country's top human rights protector is calling "a massacre" in the ancient Islamic town of Zaria.

The Shiite Islamic Movement in Nigeria said soldiers on Monday carried away about 200 bodies from around the home of leader Ibraheem Zakzaky, who was badly wounded in the attack, and demanded that the bodies be returned for the speedy burial required by Islamic tradition, according to group spokesman Ibrahim Musa.

Chidi Odinkalu of the Nigerian Human Rights Commission posted photos on social media showing a bulldozer tearing apart a Shiite shrine and said Zakzaky's home also was destroyed Zaria, located 100 miles southwest of Kano, Nigeria's second-largest city in the north.

Odinkalu told The Associated Press that Zakzaky suffered four bullet wounds and one of his wives was killed in raids that began Saturday and ended with Zakzaky's detention by soldiers on Monday morning. Odinkalu was quoting the family doctor.

Two of Zakzaky's sons also were killed and one was wounded, according to Musa.

Zakzaky and one wife have been detained by the military, according to Kaduna state Gov. Nasir El-Rufai.

Odinkalu and other human rights activists said there are hundreds of bodies at the mortuary of the Ahmadu Bello University Teaching Hospital on the outskirts of Zaria.

"Citizens must ask, who ordered this carnage?" Odinkalu tweeted.

Nigerian troops said the raids came after 500 Shiites blocked the convoy of Nigeria's army chief, and tried to kill him. Army spokesman Col. Sani Usman said the Shiites stoned the convoy. But a military report seen by the AP said the group actually opened fire on the convoy and planned to petrol bomb the vehicle of Gen. Tukur Buratai.

Maj Gen. Adeniyi Oyebade, who was in charge of the operation, told reporters Monday night that the military acted because they had reports the Shiites were gathering for an attack. "Of course, because of the report I got that they are mobilizing, I had to order that the Gyallesu (Zakzady's residence) and Hussainiya (shrine) be brought down," he said.

He said both the military and the Shiites suffered casualties and that the dead are still being counted.

Odinkalu tweeted that his friend, UNDP worker Bukhari Mohammed Bello Jega, was killed and "his young wife & child are also missing, presumed dead ..."

Outraged Nigerians took to social media to condemn "trigger-happy troops" and "extra-judicial killings."

The three areas attacked by the military remained on lockdown Tuesday, with no one allowed to enter or leave. Musa charged wounded people are being denied medical treatment by the blocks.

Iran, seen as the guardian of the Shiite Muslim faith, condemned the killings. Iranian state TV said the Foreign Ministry on Monday summoned Nigeria's charge d'affaires to demand that the Nigerian government take responsibility for the lives and properties of its millions of Shiites.

State Department spokesman John Kirby said the U.S. Embassy in Abuja is seeking information about what happened. He said the U.S. government will continue to make protection of civilians and respect for human rights "a priority in its ongoing engagement with the Nigerian government."

Nigeria's Shiites, a movement started 37 years ago by Zakzaky, who dresses in the robes and turban of an Iranian ayatollah, often have clashed with police and other security forces over their unlawful blocking of major roads to hold religious processions.

Nigeria's military is infamous for its excesses. Nigerian troops are accused of killing thousands of detainees by shooting, torture, starvation and suffocation in its prosecution of a war against Boko Haram Islamic extremists in the northeast.

The Shiites two weeks ago suffered a suicide bombing by Boko Haram that killed 22 people. Boko Haram often attacks Muslims who oppose its radical vision of Islam.

In 2009, Nigerian armed forces attacked Boko Haram's headquarters and killed about 700 people, including its leader. The group re-emerged as a much more violent entity.