Northern Ireland's population grows by 11,100
The population of Northern Ireland had increased to 1,851,600 by the middle of 2015, new figures have revealed.
It means the number of people in the province grew by 11,100 - or 0.60% - in a year.
Northern Ireland accounts for 3% of the UK's population.
The UK has passed 65 million for the first time after rising by more than half a million in the same period.
Across the UK, natural growth - more births than deaths - of 171,800 and net international migration of 335,600 helped push the number of people living in the country to an estimated 65.1 million as of the middle of 2015.
That was a jump over the year of 513,000, or 0.8%. The figures mean that the total population has increased by around 4.7 million in 10 years.
The Office for National Statistics (ONS) said the rise over the 12 months to mid-2015 was similar to the average annual increase seen in the last decade.
England saw the biggest jump in population, climbing 469,700, or 0.86%, to 54,786,300.
The population of Scotland increased by 25,400 (0.47%) to 5,373,000, and Wales rose by 7,100 (0.23%) to 3,099,100.
Population variation caused by to natural change is at its lowest level since the year to mid-2006, the ONS said.
Its report added: "The number of births has decreased on last year's figure and is below the average for the period, while there was an increase in the number of deaths since last year, partly attributed to flu outbreaks in early 2015."
An increase in immigration (up 53,700) and a smaller decrease in emigration (down 22,300) contributed to the increase in net international migration compared to that seen in the year to mid-2014.
International migration inflow is at its highest since the year to mid-2007, the ONS said, while outflow is at its lowest since comparable records began in 2002. The figures indicate migration accounted for just under two-thirds of the annual change.
In addition to the direct impact on the size of the population, current and past international migration also has indirect effects on the size of the population as it changes the numbers of births and deaths in the UK, the ONS report said.
An increase of 5,800 people in the Armed Forces and prison populations also contributed to the growth.
The figures were released hours after the polls opened in the EU referendum and came after a campaign dominated by debate over immigration.
Simon Ross, chief executive of charity Population Matters, said: "The UK population is growing faster than even the concerning trend of recent years.
"Near-record net migration and an excess of births over deaths, to which migration also contributes, are combining to keep the UK near the top of the European population growth league table."