Bahrain is holding its first parliamentary elections since 2011, when security forces cracked down on protests inspired by the Arab Spring.
But the main opposition party, Al-Wefaq, and other groups are boycotting the polls as they demand greater rights and a greater say in government.
The Gulf kingdom has been ruled by the Khalifa Sunni dynasty since 1783, in a country where the Shia community today accounts for about 70 percent of the Muslim population.
The opposition is calling for what it describes as a "real constitutional monarchy." with an elected prime minister who is independent from the ruling family.
Commenting on the opposition boycott, Sheikh Ali Salman, general secretary of the Al-Wefaq National Islamic Society, said: "What a failure it is for the government to beg for a vote from a people who are marginalised by them.
"The government is looking for the impossible from any rational person."
But Bahrain Information Minister Samira Rajab insists the government is open to talks, saying: "The door to dialogue will never be shut, and we can communicate with anyone through any channel, the doors of the political leadership are always open, that's all we can do, we can't let this country become a mess."
ISIS believes that the Shias are apostates and must die in order to forge a pure form of Islam.