Tens of thousands of people are marching in Hong Kong to express concerns about the progress of democracy since the city's return to Chinese rule 13 years ago. But the passage of electoral reforms has left the once solid democratic movement in disarray.

Pro-democracy lawmakers and activists in Hong Kong are calling for unity, a week after the Democratic Party helped pass reforms in the process for selecting the city's lawmakers and leader, known as the chief executive.

Audrey Eu, leader of the Civic Party, urged all democracy activists to set aside differences and join Thursday's march, after some called the Democratic Party's support of the reforms a betrayal.

"The first of July does not belong to any political party, it belongs to the Hong Kong people. We have to demonstrate to Beijing, to the government? that we are determined that we are going to have real universal suffrage," said Eu.

On Thursday, tens of thousands of people are to march through the central part of the city calling for universal suffrage. Large pro-democracy demonstrations have often marked Hong Kong's July 1 celebration of its return to Chinese sovereignty.

Democracy advocates have long demanded direct election of Hong Kong's leader and all of the legislature. Since the city's hand-over to China from Britain in 1997, its chief executive has been selected by a group of 800 mostly pro-Beijing representatives, while only half the legislature is directly elected.

There had been no progress on the issue, even though universal suffrage is enshrined in the city's mini-constitution and the one-country, two-systems policy governing its relationship with Beijing.

Last week, the Democratic Party broke from its allies and voted for a government reform plan, which increases by half the number of people who can elect the chief executive. It also adds 10 lawmakers to the 60-member Legislative Council, making the majority of Hong Kong lawmakers popularly elected for the first time by 2012. The government says these changes will pave the way for direct election of the chief executive by 2017 and all lawmakers by 2020.

Lawmaker Lee Cheuk-yan of the Confederation of Trade Unions said the compromise split the movement.

"The winner is the central government, of course. They have very successful splitting our vote and it's a pity. We are no closer to real universal suffrage," said Lee..

Emily Lau, Democratic Party vice-chairwoman, says her party is still fighting for universal suffrage.

"I think we remain confident that if we continue to work to public interest of Hong Kong we will, we will continue to get the trust and confidence of many Hong Kong people," said Lau.

For the Democratic Party and Beijing to be on the same side of a political issue is unprecedented, and some political analysts here say it may be the start of a pragmatic relationship.

Chief Executive Donald Tsang says the passage is a "decisive step in the right direction."