The terrorism threat level in Northern Ireland has been raised from substantial to severe, meaning an attack is highly likely.

The move, based on an MI5 intelligence assessment, follows a rise in dissident republican activity, including a recent gun attack on a top police officer. It reverses a downgrade in Northern Ireland's terror threat level last March - its first change for 12 years.

It was announced by Northern Ireland Secretary Chris Heaton-Harris. MI5, the UK's Security Service, is believed to review the threat level every six months. The terrorism threat level remains substantial in the rest of the UK, meaning an attack is a strong possibility.

Threat levels are designed to give an indication of the likelihood of a terrorist attack and there are five rankings ranging from low to critical. Severe is one level below critical, meaning an attack is expected imminently.

A British man has been arrested in Germany on suspicion of spying for Russia.

German federal prosecutors said the man - named only as David S - worked at the British embassy in Berlin.

He allegedly passed documents to Russian intelligence "at least once" in exchange for an "unknown amount" of money.

He was arrested in Potsdam outside Berlin on Tuesday and his home and workplace have been searched.

A spokesman for Germany's foreign ministry quoted by AFP news agency said Berlin was taking the case "very seriously", and said spying by "a close alliance partner on German soil is unacceptable".

The arrest was the result of a joint UK-German investigation, the statement read.

It was intelligence-led and had been going on for some time leading up to the arrest, the BBC's Security Correspondent Gordon Corera says. MI5 and other UK agencies, as well as British police, had been working with the Germans to learn as much as they could about the alleged activity.

Beijing has been accused of sponsoring an attack on Microsoft Exchange email servers earlier this year which "recklessly" exposed thousands of businesses to criminal hackers.

The Chinese government has been accused of "systematic cyber sabotage" in statements by the UK and allies, including the US and Canada.

The allies are announcing that they believe Chinese state-sponsored hackers were responsible for an attack earlier this year which "indiscriminately" compromised an estimated 400,000 servers worldwide, leaving them exposed to criminals.

More than 70 organisations in the UK were compromised by the hack, perpetrated by a group associated with Beijing according to the National Cyber Security Centre. This attribution has been supported by allies.

Foreign Secretary Dominic Raab described the hacking campaign - which is believed to have compromised the on-premise email servers indiscriminately with an intention to subsequently target specific victims - as "a reckless but familiar pattern of behaviour" from the Chinese government.

The head of MI5 is to urge the public to be as vigilant about threats from "hostile states" as from terrorism. These include disruptive cyber-attacks, misinformation, espionage and interference in politics - and are usually linked to Russia and China.

In a speech on Wednesday, Ken McCallum will say these "less visible threats... have the potential to affect us all". He will say these threats are affecting UK jobs and public services and could even lead to a loss of life.

The head of the Security Service wants to challenge the idea that activity by so-called "hostile states", usually taken to mean primarily Russia and China, only affects governments or certain institutions. Instead, he will argue, in an annual threat update, that the British public are not immune to the "tentacles" of covert action by other states.