Australian Federal Police has won its application to hold a teenager from Sydney’s west for a further 68 hours, after he was arrested during early morning counter-terrorism raids last week.

The 18-year-old was arrested in Wentworthville on Wednesday in pre-dawn raids across Sydney's west after the fatal shooting of NSW police employee Curtis Cheng on October 2.

He had gone to the same school as the shooter, Farhad Khalil Mohammad Jabar, Arthur Phillip High School, and was arrested along with four others during a series of pre-dawn raids in Sydney’s west.

The others were all later released by police, while the 18-year-old’s detention order was due to expire today.

AFP officers sought to keep the man in custody for a further 68 hours and were tonight given the go ahead by a Sydney court.