The operation is understood to relate to a possible plot involving Islamist extremists with potential targets in the UK.
The threat was not thought to be imminent.
Some of those arrested are understood to be British nationals.
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The 78-year-old woman suffered serious injuries after her bag became trapped between the doors of a train at Notting Hill Gate station.
The oil has affected wildlife and boat owners have been told not to move their vessels to avoid spreading it.
Fearing for public safety, PC Chegwin pushed her in the chest in a defensive manner, not knowing she had extensive breast surgery.