Police believe the second bomb was hidden in a motorcycle parked outside the church.
A statement by ISIS posted on social media claimed the attack was carried out by two suicide bombers who wore explosive belts, one detonating at the gate and the other in the parking lot.
Authorities are piecing together what led to the deadly blasts that occurred amid tight security.
"The perpetrators of these crimes should be brought to justice and a clear signal given that attacks of religious places of worship will never be tolerated".
Two consecutive explosions reportedly caused by improvised explosive devices (IED) killed and wounded a number of civilians and government troopers from inside and outside of the supposedly solemn place at 8:45 a.m. on Sunday (January 27).
The main road leading to the church was sealed off as there were vehicles transporting the dead and injured to hospitals. At least seven of the critically wounded were helicoptered to Zamboanga City, he said.
Finally, after thousands of lives had been lost, on October 17, 2017, President Rodrigo Duterte declared Marawi was "liberated from terrorist influence".
"The enemies of the state have boldly challenged the capability of the government to secure the safety of the citizenry in that region", said Salvador Panelo, Duterte's spokesman.
Most other Muslim areas approved the plan, aimed at ending almost five decades of a separatist rebellion that has left 150,000 people dead in the predominantly Roman Catholic nation.
Air strikes were conducted in areas surrounding Jolo, Sulu in a mission to pulverize the Abu Sayyaf Group (ASG), as authorities continued to determine whether Sunday's bombing of a Catholic cathedral was the handiwork of suicide bombers.
The main Islamist militant group is Abu Sayyaf, which has claimed responsibility for numerous horrific terror attacks that have rocked the country in recent times.
An alleged relative of one of the suspects in the bombing of the Our Lady of Mt. Carmel Cathedral in Jolo, Sulu, was killed in a shootout with police on Tuesday night.
Hours after the attack Islamic State (IS) confirmed they were responsible for the attack on Jolo Island a place known for activity from several jihadists groups.
Last week, voters approved the creation of the Bangsamoro Autonomous Region in majority-Muslim areas of southern Philippines. "Last week, there was a referendum and the island of Jolo voted to not be a part of this new autonomous government that is being created", the report said.
"May all our religions of peace guide us in our quest for a brighter future for the peoples of Mindanao".
No groups have claimed responsibility so far.
Aside from Abu Sayyaf, other militant groups in Sulu include a small band of young jihadis aligned with the Islamic State group.
The Bangsamoro, meaning Moro nation, is is expected to replace the existing ARMM, which has been criticised as merely nominal, and failed to end the violent conflict that has left at least 120,000 people dead over the past five decades.
In a statement following the barbaric act, IS said that the bombing was carried out by "two knights of martyrdom" against a "crusader temple".