Fujimori, 67, has been detained in Chile since early November. He arrived unannounced in Santiago from Japan, planning to start a presidential campaign, but was instead arrested at the Peruvian government's request.
Although his daughter, Keiko, entered his name as a candidate on Friday, the electoral court may still reject him.
Fujimori supporters chanted and waved banners reading "El Chino is coming, nothing can stop him", referring to Fujimori by his nickname on Peru's streets.
"This is a happy day. We won't accept more persecution of my father," Keiko told a crowd of about 2000 people in the capital, Lima.
Peruvian investigators have prepared a series of corruption and human rights abuse charges against Fujimori, stemming from his 1990-2000 presidency and are seeking his extradition from Chile.
Among the cases are the alleged murder by government agents of 25 people in Barrios Altos, a poor district of Lima, and La Cantuta University while Fujimori was president.
Critics accuse Fujimori of murder,
corruption and rights abuses
In Barrios Altos, the government-linked paramilitary group Colina killed 15 people in 1991, including a minor, believing them to be members of the Shining Path guerrilla movement.
The next year Colina murdered nine students and a professor at La Cantuta.
The extradition process could take six months to a year, analysts have said.
The Peruvian government formally asked Chile on Tuesday to
extradite the former president, citing 12 counts against Fujimori - 10 related to alleged acts of corruption and two alleging grave rights violations.
Fujimori is accused of corrupting officials and overseeing forced abductions, murder and torture.
He says he is innocent and is the victim of political persecution.
The former leader still has a loyal if limited following in Peru, where he is credited with reining in economic chaos and leftist insurgencies.
Until May, Fujimori was leading in voter preference polls, with 15% to 18% of the vote. Latest surveys show conservative Lourdes Flores and nationalist Ollanta Humala are neck and neck at about 21%.
Fujimori was arrested in Chile in
November at Peru's request
Fujimori resigned as president in 2000 by fax from Japan. Before arriving in Chile, the Peruvian-born son of immigrants from Japan had for five years taken refuge in Japan.
Tokyo refused Lima's requests to extradite him and he was granted Japanese nationality.
Peru holds presidential elections on April 9.
Keiko Fujimori, 28, once served as her father's ceremonial "first lady" and now lives in the United States.