Updated

LONDON (AP) — The head of Britain's domestic spy agency warned Friday that the U.K. faces potent new threats from terrorism incubated in Northern Ireland, the Middle East and North Africa.

Jonathan Evans, director-general of MI5, the country's domestic intelligence service, said in a rare public speech that attacks on the U.K. are increasingly likely to emanate from Somalia, Yemen or Belfast, as al-Qaida-linked groups flee strongholds in Pakistan.

The spy chief said the 2012 London Olympic Games will likely be a major target for terrorist attacks, and warned that dissidents who reject Northern Ireland's peace process could strike mainland British cities for the first time since 2001.

Evans said Irish republican splinter groups have access to weapons, including Semtex explosives, and funds from smuggling and drug trafficking.

"We cannot exclude the possibility that they might seek to extend their attacks to Great Britain, as violent republican groups have traditionally done," Evans said, making a speech late Thursday to security industry professionals in central London. Details of the speech were made public Friday.

While security officials have improved defenses against the threat from Islamic extremism, Evans said al-Qaida plots against Britain are "uncovered on a fairly regular basis," with officers dealing with a handful of different cases at any one time.

But he said the number of plots against Britain with links to Pakistan's tribal areas had dropped from three-quarters to about a half, mainly as a result of drone strikes against al-Qaida leaders — but also because of a sharp increase in activity in the Middle East and North Africa.

Would-be terrorists from around the world, including dozens of people either born or living in Britain, are training in camps in Somalia run by the al-Qaida aligned terrorist group al-Shabaab, Evans said.

He warned Somalia shares "many of the characteristics that made Afghanistan so dangerous as a seedbed for terrorism."

"I am concerned that it is only a matter of time before we see terrorism on our streets inspired by those who are today fighting alongside al-Shabaab," he said.

On the threat from Northern Ireland, Evans said his agency had hoped dissident violence would recede following the establishment of the province's joint Catholic-Protestant government under the 1998 peace accord.

"On the contrary we have seen a persistent rise in terrorist activity and ambition in Northern Ireland," he said.

Earlier this week, The Guardian newspaper quoted the dissident Real IRA group as saying it planned attacks in England and would focus on banks. A 1993 bomb in London's financial district killed one person and injured 44.

Evans said dissidents had mounted or attempted 30 attacks this year in Northern Ireland — including a car bombing at MI5's base in the region, which caused no serious injuries — an increase from 20 attacks last year.

Republican dissidents last made a successful attack in England in August 2001, exploding a car bomb near a shopping center in west London, injuring 11 people.

However, Evans said the priority for his 3,500 staff remains the threat from al-Qaida and affiliated groups — and securing the 2012 Olympics.

"The eyes of the world will be on London during the Olympic period and the run-up to it. We have to assume that those eyes will include some malign ones that will see an opportunity to gain notoriety and to inflict damage on the U.K. and on some other participating nations," Evans said.

Evans said his agency also was concerned about the threat from devotees of Anwar al-Awlaki, the U.S. and Yemeni citizen who has become al-Qaida's leading English-speaking voice.

The Yemen-based preacher, who helped direct the failed Christmas Day bombing of a Detroit-bound U.S. airliner, has urged followers to mount attacks of any kind against the West, not simply complex 9-11-style strikes.

"There is a real risk that one of his adherents will ... mount an attack in the U.K., possibly acting alone and with little formal training," Evans said.

Also of concern are terrorists now returning to their communities after serving jail terms, he said. "Some of those prisoners are still committed extremists who are likely to return to their terrorist activities," he said.

Though the spy chief said that many British extremists simply don't have the "skills or character to make credible terrorists," he said the public should not become complacent about the threat.

"Risk can be managed and reduced, but it cannot realistically be abolished and if we delude ourselves that it can we are setting ourselves up for a nasty disappointment," Evans warned.

The spy chief also said the discovery of 10 deep-cover Russian agents in the United States in the summer proved that traditional espionage had not ended with the Cold War.

Evans, who has previously identified Russia and China as having the most active spying operations against the U.K., said British businesses are at risk of espionage alongside traditional government and defense industry targets.

"The overall likelihood of any particular entity being the subject of state espionage has probably never been higher," he said.