COPENHAGEN (Reuters) -- Denmark's Supreme Court on Thursday added another year to the sentences of two Danish Muslims and an Iraqi Kurd convicted of planning a bomb attack in Copenhagen.

The panel of seven judges ruled that Mohammad Zaher, a Dane of Palestinian origin, and Ahmad Khaldhahi, an Iraqi Kurd, must now serve 12 years in jail. The sentence of Abdallah Andersen, a Danish convert to Islam, was increased to five years.

The three had appealed against their original sentences handed down by a lower court in November.

The men were arrested in 2006 and accused of planning to bomb Copenhagen's City Hall Square or the Tivoli amusement park to protest against cartoons of the Prophet Mohammad that were published in a Danish newspaper in 2005, and the presence of Danish soldiers in Iraq at the time.

"When punishment has to be meted out, special weight should be placed on the intent to commit terrorism as an aggravating factor," four judges wrote in the majority decision.

The ruling of the Supreme Court cannot be appealed.

Reporting by Gelu Sulugiuc; Editing by Giles Elgood.