A Palestinian leader jailed by the Israelis has been entered for next month's presidential election.
Marwan Barghouti is a popular figure on the Palestinian street
Marwan Barghouti's official papers were filed hours before a deadline for candidates to register.
The decision throws the election to replace the late Yasser Arafat wide open. It had looked as if interim leader Mahmoud Abbas would win easily.
Fatah - the main Palestinian faction - condemned the move. One spokesman called it "irresponsible".
In an initial reaction, US Secretary of State Colin Powell said that Mr Barghouti's candidacy could be "problematic" given that he is in Israeli custody.
Mr Barghouti is serving five life terms imposed by an Israeli court in June for the killing of four Israelis and a Greek monk.
An Israeli government minister said Mr Barghouti should not expect to be released early.
"Barghouti, who has commissioned bloody terrorist attacks, could be freed at the earliest in 100 years - with time off for good
behaviour," Tzahi Hanegbi told Israeli radio.
Mr Barghouti refused to recognise the court trying him, and has denied being involved in violence.
Last week, Mr Barghouti issued a statement denying he would run in the 9 January poll, and expressing support for Mr Abbas, who is also known as Abu Mazen.
But Mrs Fadwa Barghouti visited her husband in jail on Wednesday and later, outside the Ramallah offices of the central elections commission announced:
"I officially presented Marwan's candidacy for the presidential elections."
Nominations had to be in by midnight (2200 GMT) on Wednesday.
Fatah spokesman Tayeb Abdelrahim said that by running as an independent, Mr Barghouti had given up his Fatah affiliation.
"We regard Marwan's position as astonishing and reprehensible," he is quoted as saying by AFP news agency.
Polls have shown that Mr Barghouti, 45, has wide popular support among Palestinians to become their leader after Arafat's death in Paris last month.
Until now, Mr Abbas has been favourite to win the election, with Mr Barghouti's cousin Mustafa, a human rights activist, running second in the polls.
While Israel has said it would deal with Mr Abbas, ministers say they will not work with Mr Barghouti.
The BBC's Simon Wilson in Jerusalem says until this point a smooth transition appeared to be taking place to hand power to Mr Abbas - one of Arafat's trusted lieutenants.
But Mr Barghouti's nomination marks a genuine threat from a younger generation of Palestinian leaders, he says.
The new challenger cut his political teeth on the streets during the first Palestinian uprising, or intifada, in the late 1980s, while Arafat, Mr Abbas and other leaders were in exile in Tunisia.
Mr Barghouti became increasingly popular in the current intifada, by backing the use of arms to oppose Israel's occupation of the West Bank and Gaza Strip.
Earlier on Wednesday, the Palestinian militant group Hamas urged its supporters to boycott the election.
The militant al-Aqsa Martyrs' Brigades - the armed wing of the Fatah movement - has announced it is backing Mr Abbas in the election.