The British Morrisons worker who fled to Syria to join ISIS urged is recruiting fanatics to plan bomb attacks similar to those that rocked the metro system in Saint Petersburg, Russia, earlier this month.

Omar Hussain, a former supermarket security guard-turned jihadi recruiter, used the secret messaging app Telegram to urge followers to carry out their own attacks in London.

In Saint Petersburg on April 3, Akbardzhon Dzhalilov, a 22-year-old native of Kyrgyzstan, blew himself up on a busy subway line, killing himself and 13 other people. Dozens of others were injured.

Hussain, 30, reportedly gave guidance on how to make bombs to his followers on the secret messaging app.

Omar Hussain used the secret messaging app Telegram to urge followers to carry out their own attacks in London similar to the subway bombing attack in Saint Petersburg, Russia

In Saint Petersburg on April 3, Akbardzhon Dzhalilov, a 22-year-old native of Kyrgyzstan, blew himself up on a busy subway line, killing himself and 13 other people. Dozens of others were injured

He then posted a photo of a finished device, saying, 'looks like creme brulee', according to The Mirror.

Last month, it was revealed that Hussain used the app to encourage ISIS supporters to 'stab' or 'slit the throats' of 'non-believers'.

Hussain, who now refers to himself as Abu Sa'eed Al-Britani, also ordered extremists to 'rise my brother and make the kafir pay'.

According to the Daily Mirror, he wrote: 'They could buy a knife and stab a kafir (non-believer) in his guts or slit his throat.'

Weeks after the messages were sent, terrorist Khalid Masood launched his horrific attack, mowing down pedestrians on Westminster Bridge and stabbing PC Keith Palmer outside Parliament.

Those killed on the bridge include Londoner Leslie Rhodes, 75, US tourist Kurt Cochran, 54, and mother-of-two Aysha Frade, 43.

The former supermarket security guard-turned jihadi recruiter (pictured in another video message, left, and right with children) used the secret messaging app Telegram to encourage ISIS supporters to 'stab' or 'slit the throats' of 'non-believers'

Hussain was among several fanatics to use the app ahead of the attack.

In one post, jihadists outlined a list of possible victims and 'perfect targets' in Britain including politicians, Jewish schools pubs and clubs.

In the post was an illustration - titled 'Fight Them' - of an ISIS terrorist dressed like Jihadi John holding a sword in front of Big Ben, as a fireball engulfed the background with a tattered Union Flag flying in the wind.

During conversations on the app, the fanatics ordered each other to target football stadiums due to a lack of security.

They also listed different methods of attacking the matches, suggesting that fans should be targeted at the end of games.

The terrorists wrote: 'Devices can be left in around the stadium, bars, cars, buses, trains, transportation etc.

'Attacks can compromise of explosives, gun attacks, knife, martyrdom vests, CHEMICAL and any other.'

Hussain left Britain in December 2013, flying to Turkey via Gatwick, despite being a known extremist who was stopped at Heathrow airport six months earlier.

Telegram is a favourite of terrorists because it uses end-to-end encryption, making it hard for security services to hack into

Once in Syria, he began making threats against the UK on the internet using the alias Abu Saeed Al-Britani.

He warned how he would like to return to bomb Britain, and in one IS video described David Cameron as a 'despicable swine'.

Last August he appeared on BBC2's Newsnight, saying: 'I hate the UK, the only reason why I would intend to return to the UK is when I want to come and plant a bomb somewhere.'

Last year, Hussain, from High Wycombe, Buckinghamshire, urged fanatics to beat up and rob drunken revellers out celebrating in the run-up to Christmas so that they could buy knives.

In a separate blog post, he doled out advice for jihadi brides, urging them to 'cook nice food' for their husbands and 'be presentable in your appearance'.

Telegram was used by fanatics before the attacks on Nice in July 2016 and Berlin in December last year.

The platform is a favourite of terrorists because it uses end-to-end encryption, which is designed to make sure only senders and recipients can view the content of messages, making it hard for security services to hack into.

It is believed that sick videos of high profile attacks were also posted on Telegram by jihadists to 'inspire' each other, including the murder of soldier Lee Rigby in Woolwich and the 7/7 London bombings.