Ahmadinejad's victory greeted by Tehran protests

* Protests erupt over Ahmadinejad's election victory

* Interior minister says Ahmadinejad gets 63 pct of vote

* Challenger Mousavi denounces result as "dangerous charade"

By Parisa Hafezi and Fredrik Dahl

TEHRAN, June 14 (Reuters) - Thousands of protesters clashed with police after President Mahmoud Ahmadinejad won an election which his reformist challenger called a "dangerous charade".

The protests were a rare direct challenge to Iranian authorities. The result and its violent aftermath raised fresh questions about the direction of Iranian policies at a time when U.S. President Barack Obama wants to improve relations with Iran.

Supreme Leader Ayatollah Ali Khamenei told Iranians to respect Ahmadinejad's victory, which upset expectations that reformist candidate Mirhossein Mousavi might win the race.

Interior Minister Sadeq Mahsouli, an Ahmadinejad ally, declared the president had been re-elected with 62.6 percent of the vote, against 33.7 percent for Mousavi.