Bahrain's interior ministry said Tuesday it is taking legal measures against the main opposition bloc Al-Wefaq over "criminal content" published on its website and Twitter account.
Al-Wefaq frequently publishes online pictures of protests led by the Shiite majority against Bahrain's Sunni government, a key US ally.
The group accused authorities Saturday of firing buckshot and tear gas to disperse protests marking the anniversary of an Arab Spring-inspired uprising that began on February 14, 2011.
It also posted on Twitter pictures of what it said were wounded protesters, and accused authorities of carrying out several arrests.
A ministry statement said the anti-corruption and economic and electronic security department had investigated "recent statements by Al-Wefaq on its website and Twitter account for criminal content punishable under the law," but did not specifically refer to the postings over the weekend.
The opposition group is also "under suspicion of publicly inciting hatred against the government and circulating false news to jeopardise civil peace and national security," added the statement, carried by the official Bahrain News Agency.
"It had also made calls for illegal rallies and incited hatred against the interior ministry and a foreign country," the statement said, without naming the country.
Sunni-dominated Saudi Arabia is a key backer of Bahrain's ruling Al-Khalifa monarchy.
The ministry has referred the case against Al-Wefaq, which includes "violations that amounted to crimes punishable by law," to the public prosecution "in order to initiate a judicial case against the society," BNA reported.
Al-Wefaq criticised the decision, which it said aims to "end legitimate opposition and refutes (government) claims of democracy," insisting that the bloc is only "practising its natural political role" as an opponent to government policies.
Authorities are using "the judiciary to punish any political action," a statement added.
Al-Wefaq leader Sheikh Ali Salman has been behind bars since December 28 for allegedly trying to overthrow the regime.
In October, a court banned Al-Wefaq for three months for violating a law on associations.
The opposition is demanding a constitutional monarchy with an elected prime minister independent of the ruling royal family, but the Khalifa dynasty has refused to yield.