Analysts and people who knew some of the 27 Bangladeshi workers suggest they may have been influenced by three radical outfits in Bangladesh, namely:

ANSARULLAH BANGLA TEAM

Created in 2011, this banned militant group adheres to Al-Qaeda's ideology and is directly linked with Al-Qaeda in the Arabian Peninsula.

Its objectives include the radicalisation of young people, inciting active participation in a local armed struggle and seeking control of areas in Bangladesh. It is believed to be behind a series of attacks on atheist bloggers in Bangladesh in recent months.

JAMAAT-E-ISLAMI

The largest Islamist political party in Bangladesh before its registration was cancelled in 2013, it is committed to the creation of an Islamic state with a syariah legal system and the outlawing of "un-Islamic" practices and laws.

The group was founded in 1941, and many of its leaders are accused of war crimes during the liberation war of Bangladesh in 1971. Several have been convicted by the country's International Crimes Tribunal.

AHLE HADITH ANDOLAN BANGLADESH

An Islamist militant outfit led by Muhammad Asadullah Al-Ghalib, who has called for a struggle against "Islamic fallacies" and to bring about Islamic rule.

It is said to be a main source of terror financing in Bangladesh along with Jamaat-e-Islami, channelling funds for recruitment and training, and to establish mosques and madrasahs that help radicalise people.