Bahraini authorities have detained the head of the main Shia Muslim opposition group after he was summoned for questioning over unspecified violations.
The Interior Ministry said on Sunday that Sheikh Ali Salman, the secretary-general of al-Wefaq Islamic Society, had been summoned for questioning by the General Directorate of Criminal Investigation.
"Legal procedures are now being finalised ahead of referring the case to the Public Prosecution," it said in a statement, without elaborating.
A lawyer who represents al-Wefaq said the charges include incitement against the government, calling for its overthrow by force and inciting the youth to revolt, al-Wasat newspaper reported.
The ministry also said that about 2,000 people participated in Friday's march and that some "violations" had been recorded, but did not specify.
Salman was among several prominent figures who led a rally on Friday near the capital, Manama, staged to protest against last month's general elections, which the opposition boycotted.
Al-Wefaq, which was established in 2002 after an announcement of political reforms the previous year, described Salman's detention as "a dangerous and uncalculated adventure that complicates the political and security scene in Bahrain".
The island kingdom has been gripped by tension since 2011 protests led by majority Shia Muslims demanding reforms and a bigger role in running the country.
Bahrain has faced sporadic unrest since authorities quelled the 2011 protests against the Sunni-led monarchy with support from other members of the Gulf Cooperation Council.
Demonstrations have increasingly given way to bomb attacks on the security forces. At least two people were killed in two separate attacks this month.