Caught by undercover agent posing as terrorist who he met four times to discuss the horrific attack

Had planned two bombs - one on side of the church in an initial attack and another to hit first-responders

Suspect Mustafa Mousab Alowemer, 21, is said to have planned the attack on Legacy International Worship Center in Pittsburgh's north side as 'revenge' for his terrorist 'brothers'

A Syrian refugee who allegedly plotted to bomb a suburban church after pledging allegiance to Isis has been arrested.

Suspect Mustafa Mousab Alowemer, 21, is said to have planned the attack on Legacy International Worship Center in Pittsburgh's north side as 'revenge' for his terrorist 'brothers'.

When FBI officers arrested him Wednesday morning they found a series of items used for bomb-making.

These included nail polish remover, batteries, ice packs, and nails, according to the Justice Department.

Alowemer, who was born in Daraa, Syria, arrived in the US in 2016 as a resettling refugee after escaping the country's civil war. But it was not long after that he expressed his allegiance to ISIS leader Abu Bakr al-Baghdadi.

He then is alleged to have begun planning an attack on one of several locations around Pittsburgh, including Yazidi families in the city, a Shia mosque, and US servicemen, before choosing the small church.

Legacy International Worship Center describes itself as a multicultural, 'Christ-centered' ministry on its website.

Alowemer then communicated with an individual he believed to be a fellow Isis supporter, who was in fact an undercover FBI operative.

He described the church as 'Nigerian' and 'mushrikeen', an Arabic term for those who commit idolatry, and called for using a bomb big enough to 'destroy it all', according to a criminal complaint.

He gave the informant 'multiple instructional documents related to the construction and use of explosives and improvised explosive devices (IEDs)' according to a report by the Justice Department.

Legacy International Worship Center in Pittsburgh's north side area describes itself as a multicultural, 'Christ-centered' ministry on its website

He also provided copies of detailed Google satellite maps, which included hand-written markings identifying the Church and escape routes.

The pair met four times in the lead up to the planned attack, which Alowemer told the informant would take place on a Sunday.

'This operation must be done on a Sunday night in order to shock the enemies of Allah almighty everywhere and all over America,' he allegedly wrote in his plans.

Documents seen by the informant claim Alowemer was 'burning from inside' for 'Muslims in New Zealand' following the terror attacks in Christchurch in March.

He was arrested yesterday after allegedly telling the undercover officer he wanted to meet 'one more time' before carrying out the attack.

Alowemer has been charged with one count of attempting to provide material support to ISIS and two counts of distributing information relating to an explosive, destructive device in relation to the bomb plot.

'Court documents show Mustafa Alowemer planned to attack a church in the name of ISIS, which could have killed or injured many people. Fortunately, his plans were foiled by the full force of the FBI Pittsburgh Joint Terrorism Task Force,' said FBI Assistant Director McGarrity.

'The FBI takes threats to churches and other religious institutions extremely seriously and will use all our resources to stop potential terrorist attacks against them.'

Lead Pastor of the church Michael Anthony Day said: 'I am addressing the recent alleged incident regarding our church being the target of a terrorist threat. Gratefully God thwarted such a tragedy protecting our congregation and northside community.

'The terrorist was apprehended earlier today and all Isis operation for planned attacked has been destroyed (sic).'

He is expected to have a hearing in federal court on Friday.