Malaysia's doors are permanently shut to illegal immigrants detained and deported after their thumbprints are recorded through biometric means.

Deputy Prime Minister Najib Tun Razak said those detained and deported under the ongoing Ops Bersepadu crackdown against illegal immigrants in Sabah will not be allowed back into the state even if they attempt to enter via legal means.

He said Malaysian security forces were keeping a closer watch on the country's vast international sea borders to prevent deported illegal immigrants from re-entering Sabah.

"We realise some communities in these parts consider our borders as porous and they have entered and exited at will. We are ensuring there are no repeats of this," said Najib, the defence minister, after a two-day visit to the military's forward bases around Sabah.

He said some 11,686 people had been checked since the operation was launched at 3am on Aug 7 and of this, 4,634 were held for further screening. Najib said about 500 were subsequently held at the temporary immigration detention centre.

Najib said of those detained so far, 393 were Filipino nationals comprising 155 men, 147 women and 91 children. Authorities also held 106 Indonesians comprising 59 men, 36 women and 11 children and one woman from Brunei.

He said the government had not received any complaints from foreign governments about the ongoing crackdown as the illegal immigrants were treated courteously and humanely.

Najib said the crackdown was focused on illegal immigrants not holding any identification documents.

Asked about doubts voiced by some Sabah leaders on the effectiveness of the operations as it did not include foreigners holding documents obtained through dubious means, Najib said: "Let's not complicate this issue."

To another question, he said the government had not set a timeframe for the crackdown and neither had it set a target for the number of people to be detained. Najib said there are no problems in the deportation process of the illegal immigrants as officials of the affected countries were rendering their fullest cooperation to Malaysian authorities.