By Dan Whitcomb

LOS ANGELES (Reuters) - Two men charged in the Opening Day beating of a San Francisco Giants fan at Dodger Stadium, an attack that outraged the city, pleaded not guilty on Wednesday.

Louie Sanchez, 29, and Marvin Norwood, 30, who were arrested in July, four months after the March 31 attack on Bryan Stow, entered their pleas during a hearing in Los Angeles.

A Los Angeles Superior Court judge ordered both men, who were brought into court in handcuffs and jail garb, held on $500,000 bail pending a pretrial hearing on September 30, after a prosecutor said both men had made incriminating "admissions" since their arrest.

Sanchez and Norwood are charged with mayhem, assault likely to cause great bodily injury, and battery. Sanchez also faces two misdemeanor counts of battery from a separate altercation on the same day.

The beating of Stow, a 42-year-old paramedic and father of two who suffered a skull fracture and brain damage, drew national headlines and touched off a furor in Los Angeles.

Critics accused city officials and Dodgers owner Frank McCourt of failing to curb an atmosphere of intimidation and thuggish behavior at the stadium.

Stow's family has sued the team and McCourt, who has battled in court with his ex-wife, Jamie, over whether she has an ownership stake in the team.

McCourt also has squabbled with Major League Baseball, which took over day-to-day operations of the financially troubled franchise in April.

In June, the Dodgers filed for bankruptcy protection, blaming Major League Baseball for rejecting a television deal that would have given the storied franchise a much-needed injection of cash.

The filing marked a stunning fall for one of baseball's marquee teams, which moved to Los Angeles from New York in 1958.

Stow, who was placed into a medically-induced coma following the attack, has become more alert and responsive in recent days, his family said on a website dedicated to the beating victim.

He recently lifted an arm when asked and slightly lifted his left leg, and later puckered his lips to kiss his sister, the family said on the website.

(Additional reporting by Alex Dobuzinskis. Edited by Greg McCune)