THE HAGUE (AFP) - Famed worldwide for their merrymaking abilities, the Dutch on Tuesday set to preparing an "unforgettable" party for the coronation of their new king Willem Alexander on April 30.

Amsterdam hotels have already been booked up less than 24 hours after Queen Beatrix announced she would abdicate, and city hall has been overwhelmed by offers of partymaking help.

The coronation is to be held on the traditional national holiday of Queen's Day, during which public drunkenness is tolerated, and the Dutch dress up in the royal colour orange.

Nationwide, streets and canals throng with sometimes unruly crowds dressed in garish orange scarves, shirts, wigs, even clogs. Some people fall in the canals, but the good natured event in the well-organised country rarely sees serious accidents or fights.

Even Dutch Prime Minister Mark Rutte, 45, and no stranger to some of The Hague's cafes, on Monday called on the Dutch to have an enormous party on the day.

"A party that matches our feelings today," Mr Rutte said, although calling for the party not to be too extravagant because of the state of the economy.

"Amsterdam and Amsterdammers will, with all the Dutch, make April 30 an unforgettable day," city hall said in a statement soon after Beatrix said she would step down after almost 33 years on the throne.

Amsterdam spokesman Bartho Boer said Dutch people around the country had been telephoning city hall either to hold events in Amsterdam on the day or to offer their services as volunteers.

"We're expecting an extremely festive day," Amsterdam Tourist Federation spokeswoman Machteld Ligtvoet told AFP.

"There will be more people attending the party than during a normal Queen's Day," she said, adding that all hotels in the city centre were already booked up.

Amsterdam's notorious coffee shops will also see particularly brisk trade in soft drugs, consumed by the Dutch and foreigners alike, and largely tolerated on the street on the special day.

In The Hague, the seat of government, Queen's Night is the big event, with thousands thronging the streets of the reputedly staid city for live concerts, fairs and other street events.

It's no coincidence that Holland House, sponsored by Dutch beermaker Heineken, at Alexandra Palace was one of the most sought-after party venues during last year's London Olympics.

Popular daily Algemeen Dagblad noted on Tuesday that "for many subjects, the real news of the day wasn't the sovereign's abdication, but the fact that Queen's Day no longer exists."

When Beatrix became queen in 1980, her coronation day, which was also her mother Juliana's birthday, became Queen's Day. Once Willem Alexander is crowned, King's Day will be held every April 27 of his reign.

The day is the birthday of Willem Alexander, nicknamed "Prince Pils" in his youth because of his ability to drink large quantities of beer at student parties.