A Middle East extremist group is trying to exploit the World Cup's global popularity by injecting its propaganda into Twitter conversations around the tournament, young Indonesians say.

In disseminating jihadist messages via the social media tool, the Islamic State in Iraq and Syria (ISIS) and its supporters have co-opted "#WorldCup2014", the hashtag used in online chatter about the world's most popular sporting event.

A hashtag is a simple way to start an online dialogue among Twitter subscribers about common interests. It groups together Twitter conversations about a popular topic, and directs online traffic toward related discussions.

But in this case, ISIS, which is also known as ISIS, is lumping together its own hashtags – such as "AllEyesOnISIS#ISIS" – with the World Cup hashtag in an apparent attempt to expose football fans to its propaganda.

Indonesian youths say they have seen tweets in which ISIS laces its messages with the hashtag for the World Cup.

Among them are Dewi Sulistyorini, a graduate student at the University of Indonesia and Central Jakarta resident Muhammad Yuri Fatahilahi (called Fatah), 16.

"They continue to make calls to the public for jihad," Dewi told Khabar Southeast Asia.

"Therefore, everyone who is interested in '#WorldCup2014' will find ISIS's propaganda, including graphic pictures of victims or calls for jihad, stories about their fighting experience while in Iraq or Syria, and similar messages," she said.

Fatah said he had come across examples in Bahasa, Arabic, English and other languages.

"Therefore, I think this is a time for Indonesian authorities to be aware of this new method. Hopefully, the National Counterterrorism Agency (BNPT) and the Communication Ministry will continue to follow up on this," he told Khabar, adding he'd also seen calls for jihad or to help ISIS, posted on Facebook and YouTube.

"They (jihadists) try to recruit people by providing graphic pictures. For example, a few days ago, I saw a posting made by a Malaysian jihadist uploaded on Facebook. It was a bloody hand; the poster said the event was after he [had] killed one Shia in Syria. Many of my friends were commenting on this," Fatah said. "Some were amazed; some were scared."

Indonesian jihadists have one purpose, terrorism expert Solahudin said.

"They want to establish an Islamic caliphate. Many of them use radical websites, including al-Mustaqbal (owned by Jemaah Islamiyah spiritual leader Abu Bakar Bashir) and VOA Islam to support ISIS.

"Beware of this propaganda," he told Khabar. "Our history is different. Islam has coexisted in Indonesia with other religions and we should continue to do so."