Participants of the rally, dubbed the Malay Dignity Gathering (Himpunan Maruah Melayu), gathered at four locations - the National Mosque, Federal Territory Mosque, Putra World Trade Centre, where Umno's headquarters are located, and the Craft Complex - before marching towards Padang Merbok in the afternoon.
Police closed several roads in the city to traffic, while shops in Chinese-dominated neighbourhoods were closed.Small groups of people started trickling in as early as 7am, as police officers stood guard nearby. As the crowds grew bigger by noon, there were reports that some members of the media were chased out by police for asking participants "provocative questions".
A crowd of about 2,000 people moved towards Bukit Bintang and a field commander was heard shouting: "Our friends at Bukit Bintang have been arrested by the police. We are going there to help them."
The rally - organised by the National Silat Federation (Pesaka), whose head is an Umno leader, Mohd Ali Mohd Rustam - is meant to counter last month's huge demonstration by electoral reform group Bersih, which some Malay groups see as a bid by the Chinese to usurp political power.
That rally demanded the resignation of Najib over financial scandals involving state investor 1Malaysia Development Berhad (1MDB). Footage of the Bersih rally, the fourth since 2007, showed some people stomping on pictures of the prime minister.
Among those attending Wednesday's rally was Mr Haji Nasir Rasyid, 80, a retired army officer with the rank of sergeant mayor. "I am here today to show Malay solidarity, that we are still solid. I am here today for Malay dignity, for the nation and the country."
"If Bersih can show off, we can also show off. If Bersih tries to be funny, we can do even more as I am ex army,'' said Haji.
The Pesaka president has said the rally on Wednesday is to remind the people to respect their leaders and is open to all races. He has also insisted that people can wear any colour they wish.
The rally was declared legal after it was initially banned by the police.
Former prime minister Mahathir Mohamad on Tuesday called for the rally to be cancelled as it was "not fighting for Malays". Many ruling Barisan Nasional leaders, including Najib, will be in Kota Kinabalu to mark Malaysia Day on Wednesday.
Inspector-General of Police Khalid Abu Bakar, the country's top cop, left his deputy Noor Rashid Ibrahim in charge as he left for Mecca. Noor Rashid told The Straits Times that the police would deploy 7,000 personnel at the strategic points that the gathering will pass through.