Opposition groups said Wednesday they have suspended their participation in national reconciliation talks aimed at ending Bahrain's political impasse following the arrest of a prominent Shiite ex-MP.

The five groups, including the main Shiite movement Al-Wefaq, "have decided to suspend their participation in the national dialogue," a joint statement said, a day after the arrest of Khalil Marzooq on charges of inciting terrorism.

"This decision will be continuously reviewed," it said.

Bahrain's public prosecutor decided on Tuesday to hold Marzooq in custody for 30 days for further investigation.

He was charged with "inciting and advocating terrorism, and using his leadership position in a legally organised political society to incite crimes," according to a prosecution statement.

Prosecutors also accuse Marzooq of being "affiliated with (a) terrorist organisation," naming the radical February 14 Revolution Youth Coalition.

Led by Al-Wefaq, the opposition has been taking part in a national dialogue that began on February 10 aimed at ending the country's political stalemate, while keeping up street protests to call for reform.

The United States said it was disappointed the opposition was boycotting the talks, but added it would raise Marzooq's case with the Bahraini authorities.

"I think the bigger context is important here, that we are disappointed that opposition groups have suspended their involvement in the national dialogue," Deputy State Department spokeswoman Marie Harf told reporters.

"We believe that the national dialogue is an important step in a longer process that leads to meaningful reforms and that addresses the legitimate aspirations of all Bahrainis. So we'll continue to encourage everyone to participate in it."

Marzooq served as deputy speaker in the 40-member parliament before 18 MPs from Al-Wefaq walked out in February 2011 in protest at violence against demonstrators.

In March 20122, security forces in the Sunni-ruled kingdom crushed a month of protests dominated by the country's Shiite majority, which demanded democratic reforms.

At least 80 people have been killed since the Arab Spring-inspired pro-democracy protests erupted, according to the International Federation for Human Rights.