SYDNEY, Jan. 2 -- Residents and tourists in northern Australia are being warned about a growing number of crocodiles that are extra dangerous in the breeding season, authorities said on Friday.

Authorities are especially concerned after four people were killed in crocodile attacks in 2014, the highest on record.

The Northern Territory Parks Wildlife Operations (PWCNT) unit said it had received numerous calls regarding sightings of large crocodiles in the Katherine River, a popular area with tourists and bushwalkers.

"The wet season is breeding time for the estuarine or saltwater crocodile," NT Parks and Wildlife said in a statement.

"Dominant males displace other males out of their territory as they compete for the female's attention."

PWCNT said the recently raised river levels have allowed crocodiles to travel more freely and inhabit any part of the river system.

"It is therefore very important to 'be crocwise'. Don't risk your life."