Sri Lanka's President Maithripala Sirisena has pardoned a death-row prisoner who murdered a Swedish teenager just a week before he leaves office, officials said Sunday, in a move that sparked national outrage. 

Jude Jayamaha, who was convicted of killing 19-year-old Swedish teenage girl Yvonne Jonsson, walked out of Welikada prison Saturday following the highly unusual amnesty granted by Sirisena.  

Yvonne Jonsson, a dual national whose mother was Sri Lankan, was holidaying in Sri Lanka when she had an argument with Jayamaha. She was found beaten to death at a high-rise apartment in Colombo in 2005. During the trial, the court had been told her skull was fractured into 64 pieces. 

Sirisena, who is stepping down after Saturday's presidential election at which he is not a candidate, announced last month he was considering a request to grant Jayamaha a pardon, saying he had behaved well in prison and called the murder an "incident of impatience." 

Jayamaha was initially sentenced to 12 years in prison. He appealed to a higher court, which rejected his plea and instead sentenced him to death, which was reaffirmed by the Supreme Court in 2014. 

Jonsson's sister Caroline wrote in a Facebook post after the pardoning decision was announced, saying "you have chosen to pardon a prisoner convicted of premeditated murder, and in doing so undermined the highest level of judiciary in the country."  

The pardoning provoked a huge backlash among Sri Lankans. Many took to social media to condemn the act.  

Sirisena decided not to seek a re-election bid for the November 16 election and must leave soon after results are declared, a day or two after the polls. A record 35 candidates have filed nominations to take part in Saturday's presidential election, nearly twice as many as participated in the last poll in 2015. 

(With input from agencies)