Police have been granted more time to question two men arrested under the Terrorism Act 2000, Scotland Yard says.
The men, who are aged 25 and 29 and from Halifax, West Yorkshire, were arrested on Tuesday and can be held until 30 January.
Two other men, both 24, were arrested in a separate anti-terror operation at Cheetham Hill, Manchester, and are continuing to be questioned.
A fifth man, aged 32, was arrested in Manchester's Longsight area.
It is thought the Manchester operation is linked to an incident earlier this month in which a terror suspect absconded, breaching a control order.
The BBC's Home Affairs correspondent Danny Shaw said the British-born man, in his 20s, disappeared while under an order which imposes a type of house arrest on terror suspects.
Searches
He is thought to have gone abroad and is not believed to be one of the three arrested in Manchester, Mr Shaw says.
Greater Manchester Police said the operation was carried out at four addresses and three others were also searched.
Officers have liaised with representatives of the local community and produced leaflets giving information about the operation.
A police spokeswoman said: "At this stage, there is no intelligence of any planned terrorist activity in the UK and the arrests are part of an ongoing investigation."
Meanwhile, the two men from the unrelated raids in Halifax were being held at a London police station.
The pair were arrested in connection with a search for extremist material which may have been used to radicalise individuals or promote ideologies supporting terrorism, according to Mr Shaw.
The arrests were made by officers from the Metropolitan Police's Counter Terrorism Command and the West Yorkshire Police.
Police also searched four addresses in the Halifax area, one of which is thought to be in the Pellon area of the town.
A flat in north London was also searched as part of the same operation.
A spokesman for the West Yorkshire force said high-visibility police will patrol affected areas to provide reassurance.
A meeting took place between police and community leaders at the Queens Road Neighbourhood Centre in Calderdale.
Police stressed there were no links with the arrests made in Manchester.
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