However, the three-man bench chaired by Justice Mohtarudin Baki allowed the appeal of two of them to reduce their jail terms.
“We are unanimous in our opinion that the appeal on conviction has no merit. There is overwhelming evidence to implicate them in the crime and as such the conviction is safe,” he said.
Mohtaruddin, however, said the trial judge failed to reason out why there was a disparity in the jail terms of the five.
The bench reduced the 25-year jail term for two brothers, Mohd Anwar Azmi, 34, and Mohd Nurakmal Azmi, 31, to 20 years.
The brothers, together with Izwan Shameer Suzaimi, 26, tyre shop worker Muhammad Luqman Hakim Abdul Aziz, 23, and teenager Abdullah Apandi were charged with promoting acts of violence in the country.
They committed the offence at No 2, Lot 3917, Kampung Bistari, Sungai Michu, Batu 13, Hulu Langat, Selangor, between 7pm on April 24, 2015, and 1am the following day.
High Court judge Nordin Hassan last year sentenced Shameer and Luqman to 20 years and Abdullah to 12 years.
The offence under Section 130G(a) of the Penal Code carries a jail term of up to 30 years and a fine.
Another accomplice, Mohd Hafifi Tarmizi, 26, who worked as a storekeeper, was jailed eight years on Nov 16, 2015 after pleading guilty to the same charge.
He then turned prosecution witness.
Nordin said their acts not only contributed to the spread of the terrorist ideology, but could even lead to the death of civilians and destruction of property.
In his judgment, Nordin said the court accepted the testimonies of the prosecution witnesses, including a friend of the accused (who has already been sentenced) that they had gone to Gunung Nuang in Hulu Langat, near Kuala Lumpur, not for camping or socialising, but instead to conduct experiments in preparation to bomb certain areas around Kuala Lumpur.
Facts revealed that Hafifi had proposed for a leader to be appointed to head a group, similar to that of those established in Syria, to plan and destroy entertainment centres, as well as vice and gambling venues around Kuala Lumpur.
All of them, including Hafifi, then made plans to perform test explosions in Gunung Nuang, Hulu Langat, Selangor, on April 25, 2015. However, Hafifi withdrew himself at the last moment.
The five have an automatic right to appeal against conviction and sentence in the Federal Court since their case started in the High Court.
Government lawyer Wan Shaharuddin Wan Ladin said the prosecution would also file an appeal against the reduction of the jail sentence for the two brothers.