SEOUL, Feb 16 (Reuters) - South Korean prosecutors on Thursday requested an arrest warrant for the head of the main opposition Democratic Party, Lee Jae-myung, in an investigation into development projects and bribery allegations.

Lee, a former Democratic presidential candidate, is accused of being in breach of his duty over losses of 489.5 billion won ($382 million) run up by Seongnam Development Corporation during his time as mayor of Seongnam city, prosecutors said.

Lee is also accused of demanding that four companies provide 13.3 billion won to Seongnam FC while he was serving as the head of the football club in return for unlawful administrative favours in what prosecutors described as bribery.

Lee, who was mayor of the city south of Seoul from 2010 to 2018, has denied any wrongdoing.

"What I did was develop the region using the authority given to me as the Seongnam mayor following due legal procedures," Lee said. "I didn't do a single act of injustice, didn't take a single penny of dirty money."

A Seoul court needs the 300-member parliament, where the Democrats hold a 169-seat majority, to waive Lee's immunity from arrest to review the prosecution's request.

The Democratic Party denounced prosecutors' move, calling it an "unprecedented act of violence to incapacitate the opposition party and eliminate the president's political enemy."

Lee lost to President Yoon Suk-yeol, a former prosecutor-general, in the March presidential election by a margin of just 0.7%.