Dissident republican bombings are demonstrating a "developing" armour-piercing capability, the UK's terrorism reviewer has warned.
More than half the terror attacks in the EU occurred in the north last year, David Anderson QC noted.
Explosive mortar bomb-type warheads have been used against police patrols in west Belfast and Derry. In some cases, high-grade and powerful plastic explosives were used, European police chiefs said.
Mr Anderson said: "There were 22 dissident republican attacks on national security targets during 2014, ranging from rudimentary letter bombs to explosively formed projectiles (EFPs) demonstrating a developing armour-piercing capability.
"None caused injuries or fatalities."
Improvised explosives aimed at police and a firebomb attack on a hotel used for PSNI recruitment were among other threats launched by dissident republicans opposed to peace. The threat level remains severe.
A total of 109 shooting and bombing incidents were recorded in the country, according to a Europol report, out of 201 across the EU. They were the only attacks in the UK last year.
In the rest of Europe the number of terrorism incidents is decreasing, EU law enforcement agency Europol said.
According to the organisation, the UK reported an increase in terrorist attacks, from 35 in 2013 to 109 (73 shooting incidents and 36 bombing incidents) in 2014.
Europol added: "Although none of these attacks were classified in a specific terrorist affiliation, they all took place in Northern Ireland."
A dissident republican group calling itself the IRA and separate from the Provisionals claimed it carried out a mortar attack on a PSNI patrol in west Belfast in March. A similar device was also used against police in Derry in November.
The Belfast bomb was an EFP - a mortar design that has been used in the Middle East.
It contains a conically shaped warhead capable of penetrating armour and can be fired from a tripod or tube.
According to the Europol report, bomb attacks predominantly incorporated ammonium nitrate mixtures (known as fertiliser) as the main charge of larger improvised explosive devices, while smaller devices, such as pipe bombs, used different mixtures.
"In some cases, for example in mortar-type attacks, a high-grade and powerful plastic explosive was used."
