An 18-year-old man from Grangetown in Cardiff has been arrested on suspicion of terrorism offences.
South Wales Police say he has been arrested under the Section 5, Terrorism Act 2006 for assisting in the preparation of an act of terrorism.
Police said that today's arrest was not linked to any immediate threat to public safety.
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Welsh Assembly Members could see a pay increase of almost 18% next year, which would see their salary rise by almost £10,000.
Plaid Cymru are expected to stress their role in any post-election discussions and say it's a chance to make Wales matter at Westminster.
A largely cloudy start to the day with a risk of some light rain and drizzle. Brighter spells will develop this afternoon.