(CNN) -- Protesters in Bahrain marched through the streets Friday to criticize government plans to boost cooperation between the island state and Saudi Arabia.
The proposed unity plans have heightened already tense relations between Manama and Riyadh, on one side, and Tehran on the other.
Though specifics of the proposals are not clear, Bahraini opposition groups are against them because they fear the plans are the latest in a string of attempts to crush dissent.
Demonstrations in Bahrain failed to gain the traction of other Arab Spring uprisings after a government crackdown, backed by troops from nearby Saudi Arabia and the United Arab Emirates.
Bahrain and other Sunni-ruled countries in the region have accused Shiite-led Iran of meddling in the country's internal affairs and standing behind the protests, which are ongoing. Tehran has denied involvement.
Bahrain is a predominantly Shiite country, ruled by a Sunni royal family.
Bahrain's state news agency BNA reported the government will take legal action against protesters "who committed violations" during Friday's rally, organized in part by Al Wefaq, Bahrain's main Shiite opposition party.
It was not clear what laws were broken.
The same party was denied permission to rally Saturday outside a U.N. building, BNA reported.
Hours before the march, Ayatollah Sheikh Qassim criticized the push for unity during his Friday prayer sermon in Duraz village, north of Manama.
"It is clear that the proposed unity is not one meant to unify the people of the region," he said. "The people are not a herd of sheep, nor are they children or dimwitted to give up their freedoms."
Such unity is meant to strengthen the grip of the totalitarian governments and limit liberties, he added.
The small island kingdom in the Persian Gulf plays a key strategic role in the Middle East and is home to the U.S. Navy's Fifth Fleet.
Elsewhere in the region, the Arabic-language Al-Alam television network aired video of protests in Tehran, where protesters expressed solidarity with the demonstrations in Bahrain and denounced the unity plans as a "U.S.-Saudi conspiracy."
The station claimed similar protests took place throughout Iran. CNN could not confirm the report.
Leaders of the Gulf Cooperation Council met in Saudi Arabia this week for a meeting to discuss transforming their six nations into a union similar to the European Union.
The idea of integrating the GCC nations into one entity -- and replacing what exists now as simply a cooperative -- was first floated by Saudi Arabia in December.
The GCC comprises Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates.