Authorities in the UAE have arrested at least four people in what human rights campaigners said might be part of a crackdown on online dissent and a tightening of the Gulf Arab state's internet law.
Interior Ministry officials were not available for comment.
The UAE, a major oil exporter, regional business hub and US ally, has not seen the unrest that has ousted autocratic Arab rulers elsewhere. But it has shown little tolerance of dissent, detaining more than 60 local Islamists this year.
Those detainees, who belong to an Islamist group called al-Islah, are accused of having links to the Muslim Brotherhood, banned in the UAE, and conspiring to overthrow the government.
Last month the UAE tightened the law on online dissent, imposing jail terms on anyone who derides or caricatures the country's rulers or state institutions on the Internet.
Rights activists said on Wednesday that four people, including former diplomat Naji al-Nuaimi, had been arrested in the weeks since the law was amended.
Some had sympathised with the Islamist detainees, had called for reforms or had criticised the security apparatus online, but did not belong to al-Islah themselves, the activists said.
Social networking sites such as Twitter and Facebook have enlivened public debate in the UAE, which controls state media and restricts freedom of speech. Users range from ruling family members and ministers to government supporters and dissidents.
The UAE, along with Gulf neighbours Saudi Arabia and Bahrain, co-sponsored a proposal to widen government oversight of the Internet at a global telecommunications summit in Dubai this month.
The proposal, which was largely defeated following fierce opposition from a US-led bloc including the European Union, Canada, Japan and Australia, sought to include clauses in a revamped telecom treaty that would have given states the power to monitor and block online content.
In Bahrain, which has been in turmoil since pro-democracy protests led by its Shi'ite Muslim majority erupted last year, several activists have been arrested or jailed on charges including defaming the king or spreading false news on Twitter.