A judge will decide whether to release or detain six suspects arrested as part of a terror investigation.
The federal prosecutor's office said they were detained following raids on eight homes in the Charleroi area south of the capital Brussels, with police seizing several bladed weapons, some of them similar to the one used in the attack.
A judge will decide whether to release or detain the suspects further as part of a terror investigation, a statement said.
During the August 6 incident, a machete-wielding man assaulted the two women outside the main police station in Charleroi before being shot dead by a third officer.
He was identified as an Algerian living illegally in Belgium.
The IS-linked Amaq news agency said one of the group's "soldiers" carried out the attack "in response to calls to target citizens" of countries involved in the US-led coalition bombing jihadists in Syria and Iraq.
Belgian prosecutors have said the man, identified only as K.B., "had a criminal record but was not known for terrorism."
Belgium has been on high alert since suicide bombers struck Brussels airport and a metro station near the European Union headquarters on March 22, killing 32 people.
Those attacks were claimed by IS, which controls parts of Iraq and Syria and has claimed numerous terror strikes in Europe over the last year, including attacks in Paris which left 130 people dead.