Airlines cancel flights as airports experience 'major disruptions' over protests, strikes

Organizers estimated more than 150,000 people joined the demonstration, while the police put the crowd at 80,000.

Police vehicles were seen chasing protesters. Officers who were out of uniform but identified by their red arm bands detained protesters, tying their hands with plastic bands. 

At one point, police officers on bicycles sheltered inside a hotel from a large group of protesters.

The protesters have been demonstrating across Brussels center, between Gare du Nord and Gare du Midi train stations, Reuters reported. 

The protest was organized by Belgium's three major trade organizations.  

"Due to the national industrial action on Tuesday 14 October in which the staff of the security service provider is participating, we unfortunately expect major disruptions to our airport operations on that day," the airport posted on their website. 

The second-largest airport in the European country, Charleroi Airport, has also canceled flights due to lack of staff. 

Brussels Airport was in consultation with airlines in an attempt to persuade them not to operate any departing flights on Tuesday, Reuters reported. 

"As departing passenger flights are canceled, cancellations are also possible on some arriving flights," said the airport.

The airport said it expected a "busy day" on Wednesday.

The Associated Press and Reuters contributed reporting.