NEW YORK - Three city firefighters were killed while responding to two separate apartment blazes - the deadliest day for New York firefighters since the 2001 terror attacks.

Two of the victims - Lt. Curtis Meyran and John Bellew - were forced to jump from a fourth-floor window of a Bronx apartment building early Sunday as flames trapped them and four other crew members. The four other men were severely injured.

"When the fire from the third floor broke through to the fourth, they were faced with a horrifying choice," said Mayor Michael Bloomberg. "They jumped out a fourth-floor window, knowing that they would be critically injured."

In a separate incident, another firefighter was severely injured while searching for the origin of a fire at a Brooklyn home. Richard Sclafani, 37, was taken to a hospital where he later died, officials said. The deaths were the most recent tragedy for the department, which lost 343 members in the World Trade Center attack in 2001.

"Today is an immensely sad day in the history of the department," Uniformed Firefighters Association president Steve Cassidy said in a statement. "Sadly, these dual tragedies serve as a reminder to New York of the extreme dangers firefighters face."

Meyran's widow, Jeanette Meyran, reached by telephone, said, "My husband was one who would put other people's safety before his own." She said her husband loved his job and his children, ages 16, 10 and 6. "We're going to be lost without him for quite some time," she said.

Witnesses said it looked as though the Bronx firefighters were blown from the building.

Vanessa Whitehurst, 47, was asleep in her apartment next to the burning building when she was awakened by a strong smell of smoke. She got up to investigate and pulled back her window blinds to see firefighters falling from the apartment.

"The fire pushed them out the window," he said. "It was really devastating. The fire was at such a high flame, then other firefighters were coming down the fire escape like they were trying to get away."

In Brooklyn, firefighting colleagues, their faces still blackened with soot from their blaze, visited with Sclafani's family at the hospital where he died. "Richard made the ultimate sacrifice," the mayor said. "This guy was somebody that everybody loved and respected."