A Sikh-American post-doctoral fellow at New York University was called "Osama" by a teenager, in a fresh incident of racism towards members of the community.

Simran Jeet Singh, a post-doctoral fellow at NYU's Center for Religion and Media and a senior religion fellow for advocacy group Sikh Coalition, recalled the encounter in an essay on NBC News.

Singh also writes about how he did not remain silent at being called racial slurs and confronted the young black man.

Singh said he was running along the Hudson River in the city on Thursday, heading from his office at NYU to his home.

Even though he had headphones in his ears, he could could still hear someone shouting at him, "Osama! Osama!" along with another inappropriate expletive.

When he turned to see who was yelling, he saw a group of three young teenagers.

Singh said he had first decided to continue on his way but he soon recalled another incident from the past week, when an older woman had called him a different racial slur as she walked by him.

Singh had not responded to that woman but later regretted regretted not confronting her.

He said, "I told myself I would be better prepared next time. I consulted with my friends, asking how I could have responded effectively and constructively." 

"I took their advice to heart, not realising that I would find myself in a similar situation just a week later," he said in the essay.

Singh said he stopped his run and turned around and after deciding it was relatively safe, he slowly approached the teenager who had shouted at him.

The young black man avoided eye contact as Singh walked up to him.

As Singh approached him, the teenager said he was joking and apologised.

However, Singh said it is not as easy as giving an apology.

"It hurts," Singh told the young man.

"It hurts when people say racist stuff towards me. It hurts when people see me and assume I'm the enemy. And it hurts even more because you know exactly how it feels," Singh added.

"You know how messed up that is?", Singh said in the essay that he told the young man that "people in this country used to say hateful stuff to your grandparents ".

The young man again apologised, Singh said adding that he shook his hand and asked him to be more thoughtful.

Singh said in his essay that he was sharing his story "because I consider it a small victory and we all need some wins against bigotry, especially in this political climate.

"It means a lot to walk away from that exchange feeling a sense of solidarity, especially knowing how deeply rooted anti-black racism is among Asian-American communities," he said.

"It also gives me heart to realise that we can make positive change if we're willing to engage with one another on a human level," he said.