Two teenagers and a man have been arrested in separate counter-terrorism investigations.

Greater Manchester Police said a girl and boy, both aged 16, were detained yesterday by officers from the North West Counter Terrorism Unit (NWCTU) on suspicion of being concerned in the commission, preparation or instigation of an act of terrorism.

Later it emerged that a 29-year-old man from Stoke-on-Trent was arrested this morning in connection with suspected online posts referring to Islamic State.

Following the arrests of the teenage suspects, two addresses in the Mossley area of Tameside are being searched. A police spokesman said the searches - in Hanover Street and Spring Mill Drive - "are expected to last some time".

A police van was parked outside a terraced house in Hanover Street, along with a smaller Tactical Aid Unit van parked opposite.

The curtains at the front of the house were closed.

Julie Clays, a resident of Mossley for more than 20 years, said: "I'm stunned. It's a wonderful place to live and a very close-knit community. People of all sorts get along here so I'm really shocked.

"Obviously it's quite worrying and the ages of those arrested are very young, but I guess we will have to wait for more of the details."

Chief Superintendent Caroline Ball said: "I know news of an arrest made under terrorism legislation in this community will cause a certain amount of anxiety and people will understandably have questions.

"What I want to stress very clearly is that this investigation is in no way linked to any sort of international terrorist plot nor have we recovered any evidence to suggest the community of Mossley is at risk.

"This investigation has arisen as a result of information from law enforcement agencies so it is prudent we act on that information and carry out a thorough, professional investigation to determine the circumstances and details of the activity reported.

"Members of our community will see a lot of police activity at these addresses over the coming days but rather than cause anxiety I want people to be reassured that we have taken this precautionary action to ensure the safety of our residents."

Meanwhile officers from from the West Midlands Counter Terrorism Unit arrested a man at his home in Stoke-on-Trent on suspicion of encouraging terrorism and supporting a proscribed organisation this morning.

His arrest relates to "suspected online postings which reference the Islamic State", West Midlands Police said.

West Midlands Police said that the arrest was "pre-planned and intelligence led", adding that the action was not taken because of any immediate risk to public safety. It was not connected to the police activity in Manchester.

The arrests came as a man from Liverpool appeared in court in London charged with attempting to obtain the deadly chemical ricin.

Two police officers stood on guard outside a new-build three-storey house in Spring Mill Drive, Tameside.

The front door of the property was boarded up.

Neighbours said a couple and a teenage girl lived at the address.

One said: "They are just a normal family, very nice and pleasant.

"The girl seems normal enough as well. I see her all the time walking to school, wearing her headphones."

Sources at Greater Manchester Police said one line of inquiry was focused on internet activity between the two teenagers, who are said to know each other.

The arrested boy is understood to live at the address in Hanover Street.

Neighbours said the youth lived with a middle-aged woman.

Both the boy and girl are currently studying at college.