Malaysian police fired tear gas and detained over 900 people in the capital Saturday as thousands of activists evaded roadblocks to hold a protest against Prime Minister Najib Razak's government.

The opposition-backed rally was the culmination of weeks of intense pressure on the prime minister's long-ruling coalition to meet demands to make election laws fairer and more transparent.

Leaders of Bersih, a coalition of more than 60 non-governmental groups, say the rally will go on as scheduled, despite the government's refusal to issue the necessary permit.

Meanwhile, pro-government supporters are conducting their own demonstration in the capital without police intervention.

Bersih is demanding the government implement electoral reforms ahead of the next round of national elections, including measures to prevent vote-buying and fraud. The elections are due to be held in 2013, but could come earlier.