Four alleged terrorists targeted Danish Crown Prince Frederik as part of their planned revenge attack on a newspaper that printed cartoons of the Prophet Mohammed, a court heard today.

Prosecutors told the court the suspects probably intended to attack the offices of the Politiken newspaper where the crown prince was scheduled to hand out an annual sports award.

The four men - three Danish citizens and one resident of Sweden - are accused of terrorism and illegal possession of weaponry and could face 16 years in prison if found guilty.

A lawyer for one of the accused, Mounir Ben Mohamed Dhahri, said today before the trial that his client would plead guilty to the weapons violation but not guilty to the terrorism charge.

Three of the four accused were arrested in December 2010 while they were allegedly on their way to carry out a violent shooting attack on the Jyllands-Posten newspaper that published 12 cartoons of the prophet in 2005.

The fourth, Sabhi Ben Mohamed Zalouti, left the car while it was en route and returned to Stockholm, where he was arrested the same day as the others.

Surrounded by heavily armed police, the four defendants were led in handcuffs into the media-packed courtroom just outside the capital of Copenhagen.

The men - Dahri, Zalouti, Munir Awad and Omar Abdalla Aboelazm - could face 16 years in prison if found guilty, while prosecutors are expected to ask that the men be deported from Denmark after serving their sentence.

Awad, Aboelazm and Zalouti are likely to plead not guilty to both the terrorism and weapons accusations.

News of the group's alleged attack plans sent a tremor through the largely peaceful Danish society, which is attempting to lay to rest the 2005 cartoon debacle.

The trial will last approximately two months, with a verdict expected in mid-June.