Orlando, Jun 14 (IANS): Thousands of people rallied in the US city of Orlando on Monday night for the first official vigil to commemorate the victims in deadly mass shooting at a gay nightclub that left 50 people killed and 53 injured on Sunday.

People from all around the state of Florida gathered at the lawn in front of the Dr Phillips Centre for the Performing Arts, holding praying signs and candles. Some of them laid flowers and wrote encouraging words on the pavement with crayon, Xinhua reported.

"Tonight we remain a city of pain, we are mourning and we are angry," said Orlando Mayor Buddy Dyer in a speech during the vigil.

Afghan-origin Omar Mateen, 29, opened fire at the Pulse gay nightclub around 2.00 a.m. on Sunday. It was the worst mass shooting in US history and the deadliest terror attack since the 9/11 attacks in 2001.

Islamic State militant group claimed responsibility for the attack, however, the extent of its involvement is still being probed.

Hospital officials said five people were still in "grave condition".

Orlando Regional Medical Centre said 29 people were still at the hospital and a number of patients remain critically ill and in shock.

Dyer applauded the effort made by police officers, first responders and people who lined up to donate blood in the aftermath of the incident.

"We will get through this because in our city's darkest hour, our residents have shown that they are the light," Dyer added.

Many people volunteered to bring flowers, signs, food and water for the people attending the vigil.

"It's so important to do something instead sitting at home paralysed," said Eileen Simoneau, a volunteer who hands out waters at the event.

Dyer also noted the city officials had identified all 49 victims and notified their relatives.