PKR president Dr Wan Azizah Wan Ismail urged the police to explain why it had initially ruled out terrorism as the cause behind the June 28 Puchong grenade attack, only to now say it was the work of Islamic State (IS) militants.

Inspector-general of police Khalid Abu Bakar today confirmed the attack was masterminded by a Malaysian in Syria who pledged allegiance to the IS.

"The people also call upon the IGP to explain why the police's earlier statement about the attack in Puchong was not a terrorist attack but instead was allegedly done by underworld elements.

"This is extremely worrying as it raises questions as to the preparedness of the police in facing IS," she said in a statement.

Wan Azizah also urged the police to classify all attacks involving explosions as "terroristic in nature until proven otherwise".

The Permatang Pauh MP also raised concern that two of the 15 arrested in connection to the attack were police personnel.

"I must therefore ask how extensively has IS infiltrated into the Royal Malaysian Police organisational structure?" she asked.

"I urge the police to reclassify all attacks involving explosives such as C4, hand grenades and others as being terroristic in nature until proven otherwise."

Wan Azizah also urged the government, religious scholars and community leaders to condemn IS attacks and extremist ideologies.

"The government must also be firm and consistent by providing clear leadership and curb a climate that encourages extremism, racism, corruption and religious deviancy, including by learning from the recent kafir harbi episode where the government was very slow to act resulting in the rise of unhealthy polemics," she said.

The attack on the Movida bar in Puchong, which occurred in the wee hours of the morning, left eight people injured. The police had initially ruled out terrorism, saying it could be gang-related.

However, a Facebook user, linked to IS militant Muhamad Wanndy Muhammad Jedi, had posted that the militant group was responsible for the attack.

Commenting on the Movida attack, Khalid had said the weapon was an old Second World War-era ‘mini-grenade’ that was used in combat and in training. It is believed to have been brought from a ‘neighbouring country’.

However, no firearms or explosives were recovered in the 15 arrests made under the Security Offences (Special Measures) Act 2012 (Sosma) so far.

Two of the 15 arrested were low-ranking police officers - one was allegedly plotting robberies in Kuala Lumpur to fund the IS while another allegedly harboured a senior IS militant.