PETALING JAYA (THE STAR/ASIA NEWS NETWORK) - Security at all immigration checkpoints in Malaysia has been tightened following a report in The Jakarta Post that four Chinese Uighur jihadists linked to the Islamic State in Iraq and Syria (ISIS) terror group had transited in Malaysia before being arrested in Indonesia.

Immigration deputy director-general Datuk Sakib Kusmi said the department knows that not all Uighur people are genuine refugees.

"We will step up checks on these people entering Malaysia. We also need to investigate whether the four had entered Malaysia on forged passports.

"We will work with other countries to combat fake passport syndicates," he said on Thursday.

A source revealed that the four Chinese Uighur jihadists could be linked to the East Turkmenistan Islamic Movement.

"Some of them are not genuine refugees. A small group of them are linked to the East Turkmenistan Islamic Movement," the source added.

The source also said it was not the first time that Uighur jihadists have used Malaysia as a transit point before heading to other countries.

The Jakarta Post reported on Tuesday that Indonesian authorities found the four people had allegedly used fake passports bought in Thailand and flew to Kuala Lumpur before heading to Bandung in West Java.

The four took another flight to Makassar, South Sulawesi, where three Indonesian militants picked them up for a ride to Poso.

The report said the elite Detachment 88 police squad arrested seven suspected terrorists, including the four individuals allegedly from China's restive Xinjiang province, in Poso over the weekend.

The report said that foreign nationals were allegedly planning to join a terrorist cell in Sulawesi, where a number of groups and individuals, including radical cleric and convicted terrorist Abu Bakar Ba'asyir, are known to have voiced their support and had raised funds for ISIS.

An estimated 100 Indonesians are believed to be fighting under the ISIS banner in Syria and Iraq.