LOMBOK, Indonesia — The Indonesian police say they have foiled a suspected terrorist cell with the ability to use Wi-Fi to detonate explosive devices, highlighting advances in bomb-making in a country with a history of militant activity tied to the Islamic State.

Several of the suspects, who were arrested in raids last week on the densely populated island of Java, are members of Jamaah Ansharut Daulah, a local militant group that has pledged allegiance to the Islamic State, the police said.

During the raids, counterterrorism agents found bomb-making equipment and traces of triacetone triperoxide, a highly unstable homemade explosive that is sometimes used by the Islamic State outside the Middle East. TATP was used in Islamic State bombings in Paris and Brussels, as well as last month in Sri Lanka, where more than 250 people were killed by suicide attacks at churches and luxury hotels.

One of the suspects in the Indonesia plot, a skilled bomb-maker who was arrested on May 8, was perfecting the process of detonating a bomb through Wi-Fi networks, Dedi Prasetyo, the national police spokesman, said on Thursday. Mr. Dedi said that militants were planning to launch attacks on Wednesday, when the official results of Indonesia’s national elections are expected to be tallied.