Tennis paid tribute to the victims of the Paris terroristic attacks with a one minute moment of silence before the ATP World Tour Finals began on Sunday.

World No. 1 Novak Djokovic said the world has a responsibility to provide support and shelter for Syrian refugees fleeing from their war-torn nation.

Asked about the ongoing humanitarian crisis in the Middle East, Djokovic said "it's terrible, honestly, what's happening."

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"You have to get to the bottom of that, have to get to the cause. The cause is the war back in their country," Djokovic said. "You can't blame these people. If they don't have a house, have nothing, where are they going to go? Of course, they have to search for some better place to live. I think it's an obligation of all the countries to give them this right, from the International Constitution of Human Rights. It's very well written that you're supposed to offer them at least a shelter."

The United Nations High Commissioner for Refugees reports more than 4 million people have fled Syria since 2011.

Through his work with UNICEF, Djokovic has met with some of the refugees who passed through his hometown of Belgrade and reports it was a heart-wrenching experience.

"It was really touching. It was really hard for me to experience that," Djokovic said. "Honestly, I've had many of the humanitarian or charity activities in my life. I have my own foundation that focuses on education obviously. I've seen a lot because Serbia in the last 20 years has been through a lot of troubles, economic difficulties and war, and so forth. But this was one of the most hurtful emotions and circumstances I could feel, I could be experiencing.

"Honestly, playing with a child, 30 seconds later the mother comes, she takes him away from me, she says, 'We have to go, we have to leave now, we have to walk' for I don't know how many miles to get to they don't even know where."

Djokovic said such a humanitarian crisis requires a unified response.

"I'm very proud as a Serbian seeing what my people have done for these migrants, people that have suffered so much," Djokovic said. "They offer them that shelter, home, food and drink. That's the most basic things in life.

"From my perspective, I'm only an athlete, obviously I'm following this as a human being, at the end of the day we all have to be humans and feel for one another. We have to put that in front of all the laws and borders and different political stuff."

Photo credit: Camerasport