Published: 2020-02-26 18:53:08 BdST
Twenty people were killed and nearly 200 wounded in the violence, a doctor said, with many suffering gunshot wounds amid looting and arson attacks that coincided with a visit to India by US President Donald Trump.
Police and paramilitary forces patrolled the streets in far greater numbers on Wednesday. Parts of the riot-hit areas were deserted.
"Peace and harmony are central to our ethos. I appeal to my sisters and brothers of Delhi to maintain peace and brotherhood at all times," Modi said in a tweet.
Modi's appeal came after a storm of criticism from opposition parties of the government's failure to control the violence, despite the use of tear gas, pellets and smoke grenades.
Sonia Gandhi, president of the opposition Congress party, called for the resignation of Home Minister Amit Shah, who is directly responsible for law and order in the capital.
The violence erupted between thousands demonstrating for and against the new citizenship law introduced by Modi's Hindu nationalist government.
The Citizenship Amendment Act makes it easier for non-Muslims from some neighbouring Muslim-dominated countries to gain Indian citizenship.
Critics say the law is biased against Muslims and undermines India's secular constitution. Modi's Bharatiya Janata Party has denied it has any bias against India's more than 180 million Muslims.
Reuters witnesses saw mobs wielding sticks and pipes walking down streets in parts of northeast Delhi on Tuesday, amid arson attacks and looting. Thick clouds of black smoke billowed from a tyre market that was set ablaze.
Many of the wounded had suffered gunshot injuries, hospital officials said. At least two mosques in northeast Delhi were set on fire.
On Wednesday, the United States Commission on International Religious Freedom (USCIRF) said in a tweet that it was alarmed by the violence and it urged the Indian government "to rein in mobs and protect religious minorities and others who have been targeted".