A firebrand Indonesian Muslim cleric was arrested Sunday for allegedly breaching coronavirus restrictions after he held a series of sermons with tens of thousands of followers.

Rizieq Shihab's arrest came just days after Jakarta police shot dead six followers of his hardline group in a highway shootout.

Shihab will be detained for 20 days to prevent him from fleeing and destroying evidence, police said. Another reason for the detention is for him not to repeat the offence," National Police spokesman Argo Yuwono said Sunday.

If found guilty, he could face up to six years behind bars for breaching coronavirus rules.

Shihab was welcomed by tens of thousands of followers at Jakarta airport on his return from exile last month, in violation of a Covid-19 ban on gatherings.

As dozens who attended that gathering subsequently tested positive for the coronavirus, police summoned Shihab several times for questioning.

Indonesia has reported more than 600,000 coronavirus infections and over 18,500 deaths, with authorities imposing nationwide restrictions to curb the spread of the disease.

Despite those restrictions, Shihab held sermons all of which were attended by thousands of people.

The charismatic leader of the Islamic Defender Front (FPI), Shihab fled to Saudi Arabia shortly after police named him a suspect in a pornography case in 2017, and remained in exile for three years. Since his return, he's called for a "moral revolution".

His FPI is notorious for targeting night clubs and other establishments it deems "immoral", and has also attacked minority Muslim sects it considers "deviant".

He was among the main figures behind mass rallies in 2016 against the then governor of Jakarta, Basuki Tjahaja Purnama. Basuki, who is Christian, was sentenced to two years in prison for blasphemy.