More than 300 former members of the so-called Latvian Legion that fought in the Second World War on the side of Nazi Germany participated in the march.
The police also arrested several anti-fascist activists who attempted to block the march and shouted anti-Nazi slogans.
According to eyewitness reports, 150 Nazi veterans remain isolated on the central square of the capital, and the police have maintained order in the city.
On Monday, the legislature in Riga voted to ban the march, as well as protests against the former Nazi collaborators, but nationalists and radicals announced they would go ahead with the event despite official notices.
Latvian President Vaira Vike-Freiberga earlier slammed the planned marches.
"[Latvia] has set a special date, November 11, for commemorating soldiers, whereas March 16 is a kind of holiday that we really do not need," the president said. She added that it was used to attract attention to the alleged revival of fascism and Nazism in the Baltic countries, the problem that has marred their relations with Russia, which has also accused the former Soviet republics in the Baltics of what it calls unequal treatment of ethnic Russians living there.
Witnesses said several buses arrived in Riga Thursday morning from nearby villages bringing people wearing arm-bands and holding flags in preparation for the street march scheduled for 17:00 local time (15:00 GMT).
The Latvian Interior Ministry sent over 1,000 law-enforcement officers to the center of Riga to deter possible clashes between nationalists and anti-Nazi protesters during the traditional march.
Last year, 20 people were arrested in Latvia during clashes between nationalists and leftist protesters on March 16.
