LIMA - Peruvian President Pedro Pablo Kuczynski's Christmas Eve pardon of ex-president Alberto Fujimori (1990-2000) has sparked protests, and legal and medical controversy in Peru.

Many Peruvians are angry that Fujimori, 79 and ailing, was pardoned on humanitarian grounds, despite the gravity of his crimes: he was sentenced to 25 years in prison in 2009 for ordering the massacre of 25 people, among other human rights violations.

The announcement led both supporters and detractors of Fujimori to hit the streets. Sympathizers gathered outside the clinic in Lima where the former head of state is being treated for what appear to be non-life threatening ailments.

Protesters concentrated in several key plazas to denounce the pardon clashed with police, who lobbed tear gas to break up the crowds.

Legal and medical experts spoke with media about the implications of the move.

Carlos Rivera, a lawyer with the Legal Defense Institute (IDL), told reporters Sunday night he expects the questionable pardon to be contested both at home and abroad.

"They have disavowed the rulings of the Inter-American Court of Human Rights (IACHR), which assert Fujimori committed human rights violations," said Rivera.

However on Monday, in an interview with Radio Programas del Peru (RPP) news network, lawyer Mario Amoretti indicated the pardon was viable.

While a pardon would not apply in cases of crimes against humanity, he said, Peru's Constitutional Court convicted Fujimori of "qualified homicide and aggravated kidnapping, but not (crimes) against humanity."

Dr. Elmer Huerta, a cancer specialist, told RPP "the pardon is groundless" in his opinion.

"His ailments are not life threatening. None of them can take his life at this time," said Huerta, describing the measure as more of a "political pardon" than a humanitarian one.

The pardon cites that Fujimori has been diagnosed with arrhythmia (irregular or rapid heart rate) with "a moderate risk" of thromboembolism, hypertension, depression and other afflictions.

Meanwhile, several lawmakers said the pardon points to a pact between Kuczynski and political factions led by Keiko Fujimori, a daughter of the ex-president and head of the opposition Popular Force (FP) party.

The FP strongly backed a motion in congress to impeach Kuczynski for corruption. Last week, the president survived the vote.