Norway's Princess Martha Louise has married her fiance, author Ari Behn, in the ancient and picturesque city of Trondheim on Friday.

The 30-year-old daughter of King Harald V and Queen Sonja married in the medieval Nidaros Cathedral, where all of Norway's monarchs have been crowned since 1905.

What Martha and I have together is most important and that is what gives me strength

Ari Behn

Royals from across Europe gathered for the event, with Denmark's Queen Margrethe, Sweden's Crown Princess Victoria, Prince Felipe of Spain and Prince Edward of Britain among the guests.

Princess Martha is very popular in Norway for her down-to-earth attitude, but in contrast her husband has been vilified in the media as a party animal and an unsuitable match.

Horse-drawn carriage

Festivities to mark the wedding have been taking place all week in Trondheim, 380 kilometres (235 miles) north-west of Oslo, with the town decked in shocking pink and mint green - the official wedding colours.

On Wednesday, Princess Martha and Mr Behn held a private party for around 100 friends, including many of Europe's young royals. Hundreds of people gathered outside the venue to wave at the couple as they arrived.

Princess Martha will arrived at the 900-year-old cathedral in a horse-drawn carriage and was given away by her father in a solemn ceremony that began at 1600 (1400 GMT).

The city's main square will be decorated with flowers

Thousands of people lined the streets of Trondheim to view the proceedings and some lucky ones were actually inside the church - about 1,000 seats were made available to the general public.

Despite enthusiasm for the pageantry of a royal wedding some Norwegians disapprove of Princess Martha's choice of groom.

Mr Behn, the author of a book of short stories, upset some Norwegians by making a television programme showing prostitutes taking cocaine in Las Vegas.

Press attacks

The press has been particularly scathing in its criticism, questioning his suitability as a member of the royal family due to his reputation as a party animal.

The royal family has made it clear that the Denmark-born 29-year-old, described by one journalist as "a bouncer's nightmare", will not hold a title nor represent the royal house in any way.

Princess Martha voluntarily dropped her royal allowance

But Mr Behn has dismissed his critics saying, "what Martha and I have together is most important and that is what gives me strength".

Princess Martha however is extremely popular.

Earlier this year, at her own request, she dropped the "royal highness" part of her title and her royal allowance, so she could live a more normal life and run her own media group.

No name change

In a break with tradition, the royal bride is keeping her maiden name and will still be known as Princess Martha Louise, the palace announced on Thursday.

Ordinarily even royal princesses take the husband's name in Norway and she would have been known as Mrs Behn.

Princess Martha is the eldest child of King Harald and Queen Sonja, but her younger brother Prince Haakon is the heir to the throne.

The law was changed in 1990 to give princesses equal footing with princes, but the new rule only applies to future heirs, and does not include Princess Martha.