Saturday's arrest of Sheikh Jamal Abd al-Karim al-Dabaan, the mufti or religious authority for Iraq's Sunni Arab minority, sparked outrage among Iraq's Sunnis.
The Iraqi Islamic Party, whose leader is one of the country's vice-presidents, condemned it and many government officials in predominantly Sunni Salah al-din province suspended work in protest, the deputy governor said.
The US military said it had been acting on intelligence gathered following the killing of Abu Musab al-Zarqawi, the leader of al-Qaeda in Iraq, in a US air strike on June 7. It said it arrested other suspects at the mufti's home.
The Sunni Association of Muslim Scholars said that Sheikh Jamal was taken into custody, along with at least two of his sons, in the early hours of Saturday morning following a raid by US forces.
The Iraqi Islamic Party said another religious leader who had been a guest in Sheikh Jamal's home, Sheikh Abdalilah al-Hiti, was also arrested.
US forces made no mention of Sheikh Jamal's sons or Sheikh Abdalilah.
The mufti was released about seven hours later, following protests.
Hundreds of people had responded to calls broadcast over mosque loudspeakers to gather in front of the governor's office to protest against the detention, said Sheikh Yahya Ibrahim al-Atwani, deputy head of the association in Tikrit.
"[He] represents an Islamic and national symbol and these violations could cause the security situation to deteriorate," he added.
The US military said it had not known beforehand that it was the mufti's home.
The US military said one of the suspects detained was "directly associated with several senior-level al-Qaeda members and reportedly plays an important role in the network between Baquba and Tikrit".
It said troops had come under pistol fire from two suspects when they arrived at the sheikh's house, but the two were quickly overpowered and detained.
Five AK-47s rifles, 13 loaded magazines and two pistols had been recovered and destroyed on site, the US military said.
Tikrit, about 130km north of the Iraqi capital, Baghdad, is the ancestral hometown of Saddam Hussein, the former Iraqi president.
US soldiers killed
Elsewhere, a roadside bomb in the northern, oil rich city of Kirkuk killed a local intelligence chief and two of his guards, police said.
The US army also confirmed on Saturday the deaths of three US soldiers.
One was killed by a bomb blast while on foot patrol south of Baghdad, while another soldier was killed in a roadside bomb attack in the early hours of Friday morning in Baghdad.
A third died in a "non-combat" related incident on Friday afternoon, the US army said. No further details were given.