Malaysia’s largest anti-government protest in a year saw smaller crowds than a year ago and proceeded peacefully on Saturday with former strongman Mahathir Mohamad calling for the current prime minister’s ouster while a key leader was held without trial for a month under a new security law.

Several politicians and activists were also picked up after the Bersih 5 rally in Kuala Lumpur, which saw thousands held back by police road blocks set up to deter crowds in the capital city. A rival pro-government “Red Shirt” rally petered out in the afternoon as its leaders were also arrested. Fears that the two groups might clash did not materialize.

The street action did little to change the game in Malaysia’s long-running scandal over the fraud-tainted 1 Malaysia Development Bhd. investment fund. Organizers estimated about 40,000 people turned up, roughly a third the number from a similar event last year. The diminishing crowds are not large enough to bring down the government of Najib Razak, the premier at the heart of the scandal, but they are also too big to be ignored.

By using security laws and tough measures against critics, Najib appears to be winning the battle in the streets, as he clings to power despite a scandal that has spread to several countries including the United States.

“Bring down Najib Razak!” Mahathir urged the thousands gathered opposite the Petronas Twin Towers, which became the focal point of the rally after the original Merdeka Square venue was cordoned off by battalions of police in riot gear.

The 91 year old Mahathir flew back from Sudan for the rally and was clearly the star of the day, after police picked up Bersih leader Maria Chin Abdullah on Friday and announced she would be held for four weeks without trial under the new Security Offences (Special Measures) Act 2012.

Several other politicians and activists also spoke at the rally site where at least 10,000 people in yellow t-shirts sat, stood, sang and applauded Mahathir, who wore the Bersih 5 t-shirt over a long-sleeved white shirt.

Sacked deputy prime minister Anwar Ibrahim’s daughter, Nurul Izzah Anwar, spoke after Mahathir, thanking him for his presence but warning that Malaysia does not want greater authoritarianism.

Many blame Mahathir for creating the conditions for heavy-handed rule during his lengthy tenure, which ended in 2003. He prosecuted Anwar on false sodomy charges after the two became political rivals in 1998. Najib used sodomy laws to put Anwar back in jail after courts reversed the first case.

“We will never ever have another dictator in Malaysia again,” Nurul Izzah thundered to the wild applause of the crowd in a voice choked with emotion.

Electoral reform group Bersih 2.0 organized the fifth edition of the rally to press for democratic reforms, and also for Najib to step aside to allow for independent investigations into the 1MDB scandal.

Investigators in several countries including the United States and Singapore say about US$700 million was allegedly siphoned from 1MDB into the prime minister’s private bank account.

Najib, who has denied any wrongdoing, has said protests are unnecessary and blamed the unrest on his political foes including Mahathir, who broke with Najib over the scandal.

Hundreds waited overnight near Merdeka Square for the Saturday rally. This time around scores of Malays joined the protest, unlike during the previous Bersih protest, which was dominated by ethnic Chinese. The Najib government used that to describe the protest as minority dissent.

The pro-government Red Shirts counter rally failed to generate comparable numbers and police kept the two groups separated. Two Red Shirt leaders, who are also officials in Najib’s UMNO party, have been arrested. A Red Shirt supporter was also arrested for attempting to assault a Bersih 5 protester.

Tensions rose in the days leading up to the rally with police arresting several activists and politicians apart from raiding the Bersih office, ostensibly due to threats to parliamentary democracy. Bersih means clean in the Malay language.

Police road blocks in KL delayed and hampered many from turning up at Merdeka Square, prompting organizers to move to the Petronas Twin Towers site. The gleaming towers were built during Mahathir’s rule as a symbol of Malaysia’s rapid economic growth.