A Metropolitan Police spokesman confirmed a police operation was underway in the area.
Officers stormed the addresses in Barking and Newham at 4.15am this morning and confirmed "a number" of arrests have been made.
Police vehicles were pictured parked outside the Ship and Shovel pub in Barking.
Searches were continuing at both addresses, according to police.
The news comes hours after police stormed a flat in Barking connected to the London Bridge attack
Detectives in plain clothes are also at the scene, according to Sky News.
Police vans were parked outside a property on the A13 in Dagenham in east London.
James Bateman, who lives at the other side of the road, said: "At about 4am, after the large bang, I looked outside the window after being woken up and I saw about a dozen armed police officers going to and from an unmarked van."
He said they were wearing "full gear", adding: "The first bang was nothing like I'd heard before."
Mr Bateman said the bangs that followed were not as loud but sounded "the equivalent" of gunshots.
He said he thought it was more like a business address than a property where people live.
Officers were standing guard in front of the property, which is on a busy road.
Transport for London has confirmed the A13 has been shut down between the Goresbrook Interchange and Lodge Avenue Flyover while police attend the scene.
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According to local residents on social media, armed officers were followed by a helicopter escort as they moved in on the flat.
Scotland Yard have confirmed that a "number" of people have been arrested.
The raid comes amid an investigation into the London terror attack on Saturday London terror raids Sun, June 4, 2017
Police have raided a block of flats in Barking in connection with last night's London Bridge terror attack.
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As police continue their investigations following the June 3 terror attacks, a block of flats in Barking is raided for possible suspects
Twitter user BatemanLDN said: "It woke me up along with the whole street. Extremely loud bangs followed by gunshot bangs.
"All ok – very shaken residents nearby though. All quietened down now."
Simon Tucker wrote: "Heard this in the Dagenham area at around 4:15 am. Started with loud explosion sound. Followed by about 20 shots, Some sounded distant."
One Twitter user wrote: “A loud noise like an explosion has woke me up out of my sleep followed by like gun shot sounds. Anyone else in Dagenham?”
Another wrote: “Gunfire and explosions in Dagenham? Helicopters are out too. Not the wake up I was expecting.”
A Scotland Yard spokesman said: "At around 4:15am on Monday, 5 June, officers from the Met’s Counter Terrorism Command investigating the London Bridge terror attack entered two further addresses – one in Newham and another in Barking.
"A number of people have been detained and are at present being spoken to.
"Searches are ongoing at both addresses.
Morning after London attack: Heightened police presence at Borough Market & Bridge Sun, June 4, 2017
SIX people have been killed after a horrific terror attack targeted London Bridge and Borough Market on Saturday night. These are the pictures are London wakes up to the tragic scenes
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A vigil will be held for Londoners at Potters Field Park today at 6pm
This morning Metropolitan Police Commissioner Cressida Dick said "a huge amount of forensic material" has been seized.
She said they were working to establish whether the militants were supported by anyone else.
Speaking on BBC News, she said: "We do believe we know who they are"
"We are trying to find out whether anybody was helping them and to understand the background to this attack as best we possibly can.
"A very high priority for us obviously is to try to understand whether they were working with anyone else, whether anybody else was involved in the planning of this attack and to find out the background to it.
"We've carried out searches in a variety of places in east London and we've seized a huge amount of forensic material, so we're working very quickly."
The operation comes hours after police stormed a flat in Barking, east London, as part of an investigation into the London terror attack which left seven people dead and dozens injured on Saturday evening.
Police activity on Ripple Road in Barking, where officers have conducted raids
A woman is led away by police at an address in Barking, Essex
Police arrested 12 people Sunday in connection with the incident from at least two addresses in Barking.
Seven women and five men were detained by armed police as they hunted for associates of the London Bridge attackers.
Theresa May said in a speech outside Downing Street yesterday that “enough is enough” and Britain must do more to combat the threat of terror.
Labour leader Jeremy Corbyn, however, blamed Mrs May’s swingeing police cuts for the UK’s susceptibility to terror attacks, and told the prime minister national security cannot be maintained “on the cheap”.