Brazil is sending troops and extra police to the border town of Pacaraima where Venezuelan migrant camps were attacked and set ablaze.
President Michel Temer held an emergency meeting on Sunday as regional tensions rose over the numbers fleeing crisis-hit Venezuela.
Venezuela has asked its neighbour to ensure the safety of its citizens.
In Ecuador, desperate Venezuelans were reported to be crossing the border in defiance of new entry requirements.
Hundreds were stranded on Saturday when Ecuador brought in new rules requiring Venezuelans crossing from Colombia to have valid passports rather than just identity cards.
Most of the migrants are heading south to join family members in Peru and Chile.
They are seeking a better life amid a worsening political and economic crisis in Venezuela that has led to soaring inflation and chronic shortages of food and medicines.
What happened on the Brazilian border?
In Pacaraima on Saturday, several migrant encampments were attacked by angry residents following reports that a local restaurant owner had been badly beaten by Venezuelans.
There has been growing animosity towards the numbers of Venezuelan migrants entering Roraima state in recent months.
Gangs of men carrying stones and sticks set fire to tents and other items belonging to the Venezuelans, and more than 1000 migrants were said to have fled back across the border.
On the Venezuelan side, there were reports that Brazilian cars had been attacked.
Pacaraima was reported to be quiet on Sunday. Brazil's public security ministry said it was sending a contingent of 60 troops to support police in the area. They are due to arrive on Monday.
Meanwhile, the Venezuelan foreign ministry called on Brazil to give "guarantees to Venezuelan nationals and take measures to safeguard and secure their families and belongings".