Malaysian authorities have revoked the passports of 68 citizens over their involvement in Islamic State’s activities abroad, Deputy Prime Minister Ahmad Zahid Hamidi said, warning the threat from the dreaded terror outfit is real. 

Ahmad, who is also the Home Minister, said the passports were revoked two weeks ago after a directive was issued by Prime Minister Najib Razak. 

"They no longer have travelling documents as Malaysian citizens. In fact, when they come back to this country, action will be taken against them under the Immigration Act," he said on Sunday. 

The 68 Malaysians included two families which had travelled to Syria with the intention to fight for ISIS and achieve martyrdom, he said, adding the families comprised couples with children aged between 3 and 11. 

"They went to Syria to supposedly fight for IS (Islamic State), but are working as cleaners and sweepers there," Ahmad said. 

He added the ISIS threat was real, and that the government was not trying to divert the public’s attention away from other issues as claimed by certain quarters. 

"There are 10 hand grenades in the possession of the terrorists we are tracking. Two were used in the night Club bombing here last month. We do not know when or where the next (attack) is going to take place," he said. 

The minister added that security is being tightened in Malaysia, a Muslim-majority multi-racial country. 

Meanwhile, Defence minister Hishammudin Hussein on Monday urged political parties across the divide to stand united in the fight against the ISIS. 

"I am worried. The threat is real, and I will hold certain parties responsible for their words if they deny such threat. I do not think Malaysia is excluded (from being a potential target of IS attacks). 

"IS is the new phenomenon. No country in the world is spared," he warned.