ZARIA, Nigeria (Reuters) - Piles of rubble are all that remain of the residence of Nigeria's most prominent Shi'ite Muslim leader after it was demolished by bulldozers in the northern city of Zaria.
Sheikh Ibrahim Zakzaky's compound was leveled after three days of clashes between the army and Shi'ite residents of the city in December in which rights groups say hundreds of Shi'ites were killed. The army declined to give a Shi'ite death toll but said one soldier was killed and five were wounded.
The violence and its repercussions could further fracture a country battling a northern insurgency by hardline Sunni group Boko Haram, a secessionist movement in the southeast, militancy in the oil-rich Delta, as well as a growing economic crisis.
The clashes were the deadliest in living memory involving security forces and the minority Shi'ite community, say some Shi'ites and rights groups.
"We feel dehumanized and betrayed by the Nigerian government," said Muhammadu Samaru, a Shi'ite religious leader, sitting in his Zaria home. "There can never be any trust and any cordial relations between us and the soldiers unless they change their ways. This is not the first time they are killing us."
Diplomats said the violence risked spawning a radical Shi'ite militant wing - much like the Boko Haram uprising began in 2009 after security forces killed hundreds of its members and its leader Mohammed Yusuf died in custody.
Boko Haram, which has pledged allegiance to Islamic State, has killed thousands of people and driven more than 2 million from their homes in Nigeria's poor north.
After the Zaria clashes, the army detained a wounded Zakzaky. Sensing the explosive situation, the government flew him abroad for a few days for medical treatment to avoid creating a martyr like Yusuf, according to diplomats. He remains in custody.
"Whether tensions escalate or not will depend on the government's response," said one Western diplomat. "There are parallels with the start of the Boko Haram insurgency when their leader died in custody so the government needs to make sure it investigates the violence with impartiality."
Africa's most populous nation, led by President Muhammadu Buhari, is home to around 180 million - roughly evenly split between Christians, mainly in the south, and Muslims, mostly in the north and predominantly Sunni. Shi'ites are estimated to number under 4 million, according to a 2009 report by the U.S.-based Pew Research Center, but there are no official figures.
Zaria, 270 km (170 miles) north of the capital Abuja, is a predominantly Sunni city with a population of about 500,000. It is a focus for inter-community tensions because it is also the spiritual center of Shi'ite sect the Islamic Movement in Nigeria as home to its leader Zakzaky.
Human Rights Watch estimates there are around 3 million members of the sect, a religious and political movement inspired by Iran's 1979 Islamic Revolution, which would represent most Shi'ites in the West African country.
What provoked the December violence is disputed.
The army said members of the Shi'ite movement had blocked the convoy of its chief of staff, Lieutenant General Tukur Buratai, as it traveled through Zaria on Dec. 12, and tried to assassinate him. It said a shootout and street battles ensued and that it was forced to call in reinforcements.
Army officers showed Reuters pictures of guns, machetes, petrol bombs and swords with which they said sect members had attacked soldiers.
"With the Shia (Shi'ite) group ... we always have problems with those violent extremists among them, who should be brought to justice and caged," said Major General Adeniyi Oyebade, who led the army operation. "There are many moderate Shia. In the military there are Shia officers and soldiers."
But members of the sect, which says it is a peaceful movement, and some rights groups say the army launched an unjustified attack, with the motive unclear, and opened fire on civilians. Some Shi'ites showed Reuters videos on their phones of the dead and wounded.
The sect says more than 1,000 Shi'ites could have been killed - it says the army had taken more than 400 bodies to several morgues and that 750 other people were missing.
"I saw soldiers pour fuel on bodies of our brothers and set it on fire, then later they removed the bones," said 19-year old Shi'ite Aliyu Tahir, who said he was shot in the leg near the sheikh's house but managed to escape.
Zaria residents say bulldozers demolished Zakzaky's residence, a Shi'ite shrine, a prayer hall, clinic, cemetery and offices in the day and weeks that followed. A Reuters reporter saw the ruins of several sites during a visit last week.
The army declined to comment on the demolition of Shi'ite sites.
Buhari - himself a Sunni - has launched an investigation into the violence and its cause, and the destruction of the Shi'ite sites. It is unclear whether the bulldozers that entered Zaria were sent by the government or military.
The president said civilian deaths could not be justified, but also accused the Shi'ites of creating "a state within a state", though he and his government have largely declined to comment until the inquiry reports its findings, which is likely to take several weeks.
Human Rights Watch said tensions could swiftly escalate if there was any perception of bias in the inquiry, which ministers said would be conducted by an independent commission of experts.
"If no one is held accountable for this excessive military action, the risks of radicalizing some of those who lost relatives are high," said Mausi Segun, Nigeria researcher at the rights group. "This is a lesson Nigeria ought to have learnt from the killing of Muhammed Yusuf, Boko Haram's founder."
There have been sporadic clashes between Shi'ites and security forces since the 1980s in Nigeria. Zakzaky has been jailed several times, often for anti-government rhetoric.
But many Shi'ite residents of Zaria said tensions had never been this bad, and that officials' refusal to give a death toll or hand over dead bodies, as well as the destruction of the holy sites, was fuelling growing anger.
Adding a foreign dimension, the Islamic Movement in Nigeria has links to Shi'ite power Iran, which is locked in a struggle with Sunni kingdom Saudi Arabia for pre-eminence in the Middle East. Zakzaky traveled after the revolution before returning to found his sect, though the nature of the links are unclear.
Following the Zaria violence, Tehran denounced the killing of Shi'ites and urged Nigeria to protect the minority group.
Meanwhile there is deep resentment for the Shi'ite sect among some Sunni residents of Zaria who say members of the movement had regularly carried out attacks in the city in the past year - charges denied by the sect.
"They hired some thugs who came and were macheteing people," said Mohammed Bello, a Sunni who lives next to the sheikh's razed house said of one alleged attack.
While he was talking an angry crowd gathered, with many telling similar tales. "They macheted two of our motorcycles. When I tried talking to them they wounded me here on my head," said Salisu Mohammed, another Sunni.
The army detained more than 200 of Zakzaky's followers along with the sheikh after the clashes. Some other members of his sect have left Zaria or gone into hiding.
In a sign of the tensions gripping the city, several anti-Shi'ite slogans have sprung up in recent weeks on buildings used by the sect, some denouncing those detained.
"We're glad they are gone. We want them out of Nigeria," said Idris Mohammed, a Sunni living in the neighborhood of the sheikh's destroyed compound, where walls are daubed with slogans reading "Do not release Zakzaky".
Editing by Pravin Char