The main suspect, a known history-sheeter Popat Shinde, has sustained over 50 percent burn injuries when he allegedly set afire Additional District Collector of Nashik Yeshwant Sonawane, who was charred to death on the spot.
Shinde has been admitted to a local hospital for treatment, police said.
The others nabbed include Kunal Shinde, the son of the prime suspect, Raju Shirsat and Kachru Suvaralkar.
"They were arrested from the outskirts of Nashik city while attempting to escape and trying to get medical aid," Manmad police in-charge Shaikh Rafique said.
The grisly incident that sent shockwaves through the state happened on the outskirts of Malegaon town in the Nashik district.
Sonawane, along with his driver Kailash Gawli and secretary Raju Kale, earlier in the day went to raid a warehouse at Panewadi from where petrol and kerosene robbers and adulterators were reported to be operating.
According to District Collector P. Velrasu, while the raid was under way, the gang of petrol mafia attacked Sonawane, doused him with petrol and kerosene and set him on fire.
Sonawane, 44, was burnt to death within minutes while his stunned aides summoned the local police and district officials.
The gang also attempted to douse and burn Gawli and Kale, but they managed to escape to safety.
Rafique said the police were investigating the petrol mafia's links in and around Manmad, Malegaon and Nashik areas where they are believed to be active.
Meanwhile, state Tourism Minister Chhagan Bhujbal, who is also the guardian minister of Nashik district, told mediapersons that the culprits would be dealt with most severely.
A grim Revenue Minister Balasaheb Thorat vowed to try the culprits under the stringent Maharashtra Control of Organised Crime Act (MCOCA).
Chief Minister Prithviraj Chavan and Deputy Chief Minister Ajit Pawar strongly condemned the incident and assured immediate action against the gang.
Sonawane is survived his wife, who lives in Malegaon, and their two children who are students in Pune.
In a related development, all officers and staff of the state revenue department have decided to strike work Thursday to protest the incident, an employees union official said.
State Government Employees Association general secretary G.V. Kulthe said the shocking incident highlighted the might of the mafia and the vulnerability of government servants doing their duty in different parts of the state.
Kulthe urged the government to provide adequate protection to government staff while on duty in hazardous conditions and in dangerous areas to prevent occurrence of such attacks and incidents.