Security agents detained a rights activist Sunday in the northern United Arab Emirates as part of an apparent widening crackdown on perceived opposition figures, a family member and a watchdog group said.

The detention is the second in less than a week in the emirate of Ras al-Khaimah and reflects stepped up pressures by UAE authorities on Islamist groups, social media activists and others considered to be potential foes of the country's network of ruling clans.

Although the UAE has not faced street protests linked to last year's Arab Spring uprisings, security officials have increasingly targeted web sites and groups urging a greater role for the public in the nation's affairs. Authorities also have warned about the possible expanding influence of Islamist ideology that could clash with Western-friendly policies in the Gulf.

In the latest incident, activist Saleh al-Dhufairi was led away by security agents after prayers at a mosque in Ras al-Khaimah, the most northern of the seven semiautonomous emirates comprising the UAE, said his son Hassan.

The elder al-Dhufairi was arrested by authorities last month for web postings critical of state security operations, then released. He was referred to a state security court on charges of attempting to "stir sedition and abuse religion," according to the state news agency WAM at the time.

UAE officials had no immediate comment on Sunday's detention.

The London-based Emirates Center for Human Rights urged authorities to grant al-Dhufairi immediate access to legal counsel and make his whereabouts known.

"The UAE authorities are acting with impunity and with a complete disregard for the rule of law," said a statement by the group.

Last week, a member of Ras al-Khaimah's ruling family was placed under full-time guard in a palace for apparent affiliation with an Islamist group calling for more political openness in the UAE, according to relatives. It remains unclear, however, whether authorities will try to bring formal charges against Sheik Sultan al-Qasimi, a cousin of the Ras al-Khaimah ruler.

Six other pro-reform activists — some of them members of the same Islamist group, known as al-Islah, or Reform — also are being held by UAE officials after being stripped of their citizenship for criticizing the country's rulers.

Last year, five political activists, including a prominent blogger and an economics professor who has frequently lectured at Abu Dhabi's branch of the Sorbonne university, were convicted of anti-state crimes after signing an online petition calling for a greater public voice in the country's affairs.

They were freed on a presidential order, but the charges against them have not been officially dropped.