A group of Indonesian "cyber warriors" sit glued to screens, as they send out messages promoting a moderate form of Islam in the world's most populous Muslim-majority country.

Armed with laptops and smartphones, some 500 members of the Nahdlatul Ulama - one of the world's biggest Muslim organizations - are seeking to counter the Islamic State group's extremist messages.

"We'll never let Islam be hijacked by fools who embrace hate in their heart," tweeted Syafi' Ali, a prominent member of the NU's online army, a typical message to his tens of thousands of followers.

They are trying to hit back at IS's sophisticated Internet operations, which have been credited with attracting huge numbers from around the world to their cause.

Jakarta suicide bombing

Internet propaganda is believed to have played a key role in drawing some 500 Indonesians to the Middle East to join IS, particularly among those living in cities where it is easier to get online.

The dangers of the growing IS influence in Indonesia were starkly illustrated in January when militants linked to the jihadists launched a gun and suicide bombing attack in Jakarta, leaving four assailants and four civilians dead.

It was the first major attack in Indonesia for seven years, following a string of Islamic militant bombings in the early 2000s that killed hundreds.

As well as firing off tweets, the NU members have sought to dominate cyberspace by establishing websites promoting the group's moderate views, an Android app and web-based TV channels, whose broadcasts include sermons by moderate preachers.

The initiative has been building momentum for a while but started to pick up pace a few months ago. A handful of cyber warriors operate from a small office in Jakarta, while the rest work remotely, and the group mostly communicate with one another over the web.

But it will be an uphill battle and the NU, which has been promoting moderate Islam for decades, conceded they have previously struggled to take on IS's hate-filled messages.

"NU has for a while wrestled with this radical propaganda," said Yahya Cholil Staquf, secretary-general of the NU, which claims at least 40 million followers.

"Every time we defeated them, it didn't take long for them to regain their strength."

The online drive comes as the NU is set to take its campaign to promote their tolerant form of Islam onto the international stage this week, with a two-day meeting from Monday of moderate religious leaders from around the world.

Organic growth

They aim to showcase their particular brand of the Muslim faith, known as "Islam Nusantara", to counter the IS jihadists' radical interpretation of Islam.

Meaning "Islam of the Archipelago" - Indonesia is the world's biggest archipelago, comprising over 17,000 islands - it is accepting of diversity and stresses nonviolence.

It grew up organically in Indonesia, as the religion entered the country gradually and had to mix with existing traditional beliefs such as praying at tombs, making it a naturally tolerant form of Islam.

Nowadays, most of the approximately 225 million Muslims in Indonesia practice a moderate form of Islam.

The NU wants to persuade Muslims from around the world to look for inspiration to Indonesia, where religious minorities and a multitude of ethnic groups mostly coexist harmoniously, rather than to harsher forms of Islam from the Middle East.