The blaze, fanned by strong winds, broke out on Thursday evening in the affluent El Campanar district.

Police had revised the number of dead to nine from 10 on Friday in the process of identifying the bodies in the building, but confirmed a 10th fatal victim had been found on Saturday.

Outside the charred building, a single white flower was taped to a utility pole as Valencians gathered at the scene to pay their respects.

Pilar Zamora, 53, who travelled across town with her husband, said she was feeling "a lot of pain and anger".

"Seeing (on TV) people on the balcony, shouting for help and not being able to do anything...those were very difficult moments," Zamora said, holding back tears.

Her husband, Vicente Palaes, 55, said he had no words to describe how he felt when he approached the building: "When I saw it, I started to cry."

Around 100 survivors are being housed at a local hotel as they wait for a more permanent solution.

At midday on Saturday - the second of three official days of mourning decreed after the fire - hundreds of people gathered outside Valencia's City Hall for a moment of silence as flags flew at half-mast.

At the city's San Miguel y San Sebastian church, Catholic priest Juan Andres Talens said people had been praying for those affected.

"We are mourning," Talens said as a mass took place inside the historic church.

Emergency services said the blaze began on the fourth floor of one of the towers. A local magistrate has opened an investigation into the blaze.

The building, comprising two towers, was completed in 2008, officials said. It had 138 apartments, newspaper El Pais reported.

A lack of firewalls and the use of polyurethane, a plastic material, on the facade of the building would have contributed to the rapid spread of the blaze, Esther Puchades, a representative of insurance inspection agency APCAS, told RTVE, in comments evoking memories of the deadly Grenfell Tower fire in London in 2017.

The association for the polyurethane industry said in a statement no polyurethane was used in the building's cladding.

Locals have urged the authorities to ensure other buildings in the city are not at risk.

"If any building has the same cladding, now is the time to investigate and remove it," Zamora said.

(Reporting by Catarina Demony, Marco Trujillo; Writing by Jessica Jones and Catarina Demony; Editing by Alex Richardson)

By Catarina Demony and Marco Trujillo