After at least 34 people died in bomb attacks in Brussels on Tuesday, operators of major international airports in Japan tightened security and some passengers taking flights to Europe expressed unease about what happened.

"We urged security personnel this morning to beef up patrols around the airport in light of yesterday's case," a spokeswoman of Tokyo International Air Terminal Corp., the operator of the international terminal at Tokyo's Haneda airport, told The Japan Times on Wednesday.

Keisuke Hamatani, a spokesman for New Kansai International Airport Co., the operator of Osaka's main airport, said the firm has instructed security guards to heighten vigilance for suspicious individuals and objects.