Al-Wefaq officials said it was unclear whether Salman and been charged with any offense. They accused prosecutors of using illegal measures to hold him, the BBC reported.
Al-Wefaq, the main opposition party in Bahrain, won 18 parliamentary seats in the last election in 2010 but the members resigned from the legislature in 2011 following a deadly crackdown on pro-democracy demonstrations.
Al-Wefaq said a number of people were arrested Saturday while protesting outside Salman's home. Police used an "excessive amount of toxic tear gas" against the demonstrators, al-Wefaq said.
Authorities had no comment on the detention of Salman, the BBC said.
NBC reportedly holds celebs hostage to Jimmy Fallon's show
Ray Liotta sues skin care company over use of likeness