Police in the global gambling hub of Macau have arrested five people involved with an informal poll to measure support for direct elections of the Chinese-controlled city's leader.

Jason Chao, president of the Open Macau Society and one of the poll organisers, said he and four others were waiting for authorities to decide whether to prosecute them after being arrested for disobeying government orders not to collect residents' personal data.

The arrests are "a serious violation of human rights," Chao said on Monday. "You can feel that how the government fears the result of the referendum."

Reports said the five were arrested on Sunday, a day before activists kicked off the week-long unofficial referendum inspired by a similar vote in June in nearby Hong Kong that Beijing denounced as an illegal farce but which drew nearly 800,000 votes.

Macau's government privacy watchdog had warned organisers they were violating the privacy law by collecting identity card data from voters.

Al Jazeera's Rob McBride, reporting from Macau, said that the government has become "sensitive" about public displays of protest and disorders in the streets against authorities.

"What people here are talking about is also having an actual vote," he said.

'One country, two systems'

Macau was a former Portuguese colony before coming back under China's control in 1999, two years after Beijing regained Hong Kong from Britain.

The two cities are specially administered regions of China that have a broad say over their own affairs under the principle of "one country, two systems" but whose leaders are chosen by small committees of Beijing-friendly elites.

A 400-person election committee is widely expected to re-elect the current leader to another five-year term on August 31, the same day that referendum organisers plan to release results of the poll.

Public discontent is rising in Macau, the only place in China where casinos are legal, after a decade-long casino boom that supercharged the economy but also widened inequality, strained resources and inflated housing prices in the city of about 600,000.

Source: Al Jazeera and agencies