A United States postal worker was shot and wounded during an attempted robbery Tuesday afternoon in Kilbourn Park on the Northwest Side.

The postal worker, 52, was in the 3200 block of North Kildare Avenue when he was approached by two suspects who tried to rob him about 3 p.m., Chicago police said.

One of the suspects pulled out a gun and shot him in the leg, police said. He was taken to Illinois Masonic Medical Center in critical condition.

USPS postal inspectors were sent to investigate and urged people to stay away from the area.

No arrests were made.

Robberies of mail carriers have tripled in the last three years.

Elise Foster, president of the National Association of Letter Carriers branch in Chicago, said the U.S. Postal Service hasn’t done enough to address it.

Criminals target letter carriers for their master keys that unlock mailboxes throughout a ZIP code. With those keys, they can steal mail, allowing them to wash and rewrite checks, or sell the keys to other criminals.

In June, a postal worker was robbed at gunpoint while delivering mail in the Beverly neighborhood.

On Monday, thieves used a saw to cut open a public mailbox outside a post office in south suburban Orland Park. Police urged anyone who used the mailbox at 9500 West 144th Place to monitor their accounts for unusual activity.