Thousands of Feyenoord fans have packed the square outside Rotterdam city hall to celebrate their team’s first Dutch football league title in six years.

Supporters started taking their places on the Coolsingel before 7am, five hours before the team is due to appear on the balcony after receiving official congratulations from mayor Ahmed Aboutaleb.

Schoolchildren in the city who are not sitting exams on Monday have been given the day off after the council said they “should have the opportunity to experience the celebrations live”.

National train operator NS has advised people who are not travelling to the festivities to delay their journey to avoid being confronted by “large numbers of very excited Feyenoord fans on the train”.

NS expects the busiest times to be between 9am and 11am and from 2pm to 4pm, after the end of the official celebrations at 1.15pm.

The city council has published a long list of restrictions for people wanting to join the crowd. Spectators can take their own food or drink, but not in hard plastic containers and with a maximum of a litre of liquid.

Alcohol and fireworks are banned and revellers can only bring one cigarette lighter and one flag – on a pole no more than 1 metre long and with a maximum circumference of 20mm. The list of prohibited items also includes selfie sticks, drums, vuvuezlas, umbrellas, large quantities of confetti, and nail varnish.

On Sunday supporters packed Stadhuisplein following the 3-0 win over Go Ahead Eagles in De Kuip stadium that secured the Eredivisie with two matches to spare.

Fans also hung a 25-metre banner from the railings outside Paleis Soestdijk in Baarn, near Utrecht, in a gesture aimed at King Willem-Alexander, who recently admitted to being a fan of rivals Ajax.

Police made around 100 arrests in Rotterdam on Sunday for offences including setting off fireworks, drug possession, drunkenness and verbal abuse. Riot squads and water cannons were used to disperse the last of the crowds at around 8.30pm.