Home Minister Datuk Seri Dr Ahmad Zahid Hamidi has warned terrorists from Sulu against threatening to re-enter Sabah, with the aim of seeking revenge.

He said the Royal Malaysian Police (PDRM) and the Malaysian Armed Forces (ATM) on duty in the East Sabah Security Command (Esscom) were always in a state of readiness to face any threat from the Sulu terrorists.

"Don't try to threaten us. Don't try to do anything because it is not just the police and army, but also the people of Malaysia who will rise to oppose the threat from the terrorists from Sulu," he said.

He was speaking to reporters after handing over contributions for Ramadan to 455 poor and handicapped in the Rungkup state constituency here Saturday.

Ahmad Zahid was commenting on an investigation by the Sabah police over a letter which was allegedly written by Sulu terrorists who threatened to return to Tambunan, Sabah to seek vengeance.

Sabah Police Commissioner Datuk Hamza Taib was reported to have said the police had detected the source of the letter although it was suspected that it was not connected to the intrusion by terrorists from Sulu in Lahad Datu early this year.

According to the report, the letter dated July 3 and signed, 'Militant Commando' on behalf of the so-called Sulu Sultanate, was sent to the Tambunan district officer, police and the community in Tambunan, warning they (the terrorists) wanted to start a war in the Tambunan district in August.

Ahmad Zahid said there were numerous rumours, including the planned entry of Moro National Liberation Front (MILF) chairman Nur Misuari into Sabah.

"Don't listen to rumours. They will not tell us earlier, if they want to intrude into the country. If it is true they want to enter in August, we will start waiting from July," he said.

Nevertheless, the minister reminded the people of Sabah not to treat the 'outside threat' lightly because the terrorists from Sulu were notorious for their culture of seeking revenge.