The 64-year-old Nobel Peace laureate has already been in detention for 14 of the last 20 years, mostly under house arrest. The new detention sentence means she will be removed from the political scene during the army-run elections next year in Myanmar, which is also known as Burma.
The charges stemmed from a mysterious incident in which an American, John Yettaw, swam to Suu Kyi's lakeside home in May and stayed there uninvited for two days, which breached the terms of her house arrest and broke a security law protecting the state from "subversive elements."
The term was less severe than the maximum sentence she faced -- five years in prison -- and shorter than the one the court initially ordered Tuesday -- three years with hard labor.
The ruling drew immediate criticism from world leaders, including British Prime Minister Gordon Brown who called it "monstrous." French President Nicolas Sarkozy urged the European Union to adopt new sanctions, deeming the verdict "brutal and unjust," quoted the AP.
And a statement from U.N. Secretary-General Ban Ki-moon said he strongly deplored the ruling.
"Unless she and all other political prisoners in Myanmar are released and allowed to participate in free and fair elections, the credibility of the political process will remain in doubt," the statement said, according to Reuters.
"I look forward to working with you in the future for the peace and prosperity of my country and the region," Suu Kyi said in a soft voice to diplomats seated nearby, reported the AP. She then was led out of the courtroom.
Officials who spoke under condition of anonymity because of the sensitive nature of the case said she was driven back to her lakeside villa in a six-car convoy, according to news agencies.
The court also convicted Yettaw, 53, and sentenced him to seven years for breaching Suu Kyi's house arrest, for an immigration violation and for swimming in a restricted zone, according to Reuters.
The Falcon, Mo., resident was returned to Insein prison, the site of the trial, on Monday night after hospitalization for epileptic seizures.
Suu Kyi's trial has sparked an international outcry along with calls for her release and that of Myanmar's more than 2,000 other political prisoners.
After the sentence was read, Myanmar's Home Minister Maj. Gen. Maung Oo entered the courtroom and announced that read aloud a special order from junta chief Senior Gen. Than Shwe, cutting the sentence in half and saying it could be served at home.
Than Shwe's order, signed Monday, also reduced the sentences of Suu Kyi's two female house companions, Khin Khin Win and Win Ma Ma, to 18 months, the AP reported. Both are members of her political party.
---- Compiled from wire reports and other media sources