HONG KONG—The political system in Hong Kong is increasingly paralyzed, and street protests are growing more confrontational as public dissatisfaction on economic issues and a lack of democracy is rising. At the same time, the pro-democracy movement here has splintered, weakening its ability to press for changes.

Protesters, many of them young people proclaiming their interest in democracy, have opposed building an expensive high-speed rail link to Shenzhen and Guangzhou in mainland China. They are also upset that Hong Kong's mostly unelected legislators approved the measure.

The demonstrations also reflect frustration on the part of the pro-democratic parties in the former British colony that accuse China of having delayed or backtracked on commitments it made in the 1990s to allow people to directly elect a majority of lawmakers in the territory's Legislative Council.

Donald Tsang, the Beijing-backed chief executive of Hong Kong, has suffered a significant decline in his approval ratings in recent polls in recent months as he has grappled with rising local discontent.

Until recently, Hong Kong had a tradition of orderly political protests that were uncommonly polite by international standards. When 500,000 people took to the streets in 2003 to oppose successfully the introduction of stringent internal security regulations, the police did not make a single arrest.

Protests in the last few weeks, however, have been coarser. Youths have shouted obscene curses at police officers. Scuffles with officers have resulted in a series of arrests.

“;We're just sick of going to rallies that political parties organize, and we hold our banners and don't accomplish anything,”; said Christina Chan, a 22-year-old graduate student in philosophy who was arrested at her home this month on suspicion of assaulting police officers at two rallies. Released on bail of 500 Hong Kong dollars, or $65, she has not yet been formally charged and has denied any wrongdoing.

Under the terms of its transfer to Beijing's rule, Hong Kong retains broad civil liberties but also a political system that gives much greater weight to the votes of the economic and social elite. Analysts say there is limited opportunity for youths to vent their unhappiness with dwindling social mobility, high unemployment, sharply rising university tuition and an urban planning process dominated by real estate developers.

Young people have borne the brunt of competition from low-salaried employees in mainland China. They face rising competition for jobs in Hong Kong itself as banks and other high-paying employers increasingly hire mainland college graduates with family connections in Beijing.

“;This has been building for months, and I think we're heading for even greater frustration,”; said Michael DeGolyer, the director of the Hong Kong Transition Project, a coalition of academics who have traced the territory's political evolution for 22 years.

But the five pro-democracy political parties in the political opposition in Hong Kong have split deeply over tactics this winter, including a move by two of the parties this week to bring about by-elections.

Five lawmakers from two pro-democracy parties submitted letters of resignation on Tuesday that are to take effect at midnight on Thursday. Unless withdrawn before then, the resignations would prompt by-elections that the five hope to turn into an informal referendum on introducing greater democracy before the next elections in 2012, instead of waiting until 2017 or later, as Beijing officials have demanded.

Audrey Eu, the leader of the pro-democracy Civic Party and one of the five resigning, said that she believed that unhappiness with the city's economic troubles could be effectively channeled into support for democratic reforms. “;People are beginning to see it is really tied to our political system,”; she said.

But the other three parties—including the Democratic Party, the largest in the pro-democracy movement—have questioned the wisdom of this and have chosen not to have any of their lawmakers resign. Albert Ho, the chairman of the Democratic Party, said that he did not believe that dissatisfaction with the economy would show up in by-elections.

If the resigning lawmakers win their seats again in the by-election, then the Beijing-backed executive branch of the government here will dismiss the results as meaningless, Ho warned. But if any of the lawmakers loses his or her seat, then the government will seize upon the results as evidence that public support for greater democracy is limited, he said.

“;If we embark on this project, we would be in a no-win situation,”; Ho said.

Tsang, the chief executive, said in a statement on Tuesday night that the government would not recognize the results of the by-elections as a referendum. He cautioned that “;Many see it as an abuse of the by-election mechanism and a waste of public resources.”;

Beijing's main representation here, the Hong Kong and Macao Affairs Office, condemned the resignations on Jan. 15 as only likely to cause more “;social conflicts.”;

Economic worries here have crystallized around a plan to spend 67 billion Hong Kong dollars, or nearly 10,000 Hong Kong dollars per resident, to build a high-speed rail link across the border to Guangzhou. Backers of the rail line, including the government and the city's economic elite, see the link as essential to tying the city into the mainland's rapidly improving rail system and its vibrant economy, growing at 10 percent a year.

Critics of the rail line call it expensive at a time when the government is effectively raising university tuition, looking for ways to limit assistance to all but the poorest senior citizens and still mulling how to introduce a minimum wage.

Half the legislature is elected by the general public, but the other half is chosen by so-called functional constituencies—groups ranging from Hong Kong banks to the city's lawyers. Only 800 people in this city of seven million are allowed to vote for the chief executive, although most of the 800 are in turn elected by the same functional constituencies that control half the legislature.

Eu said she believed that the by-elections could become an informal referendum on whether to eliminate functional constituencies and introduce the principle of one person one vote.