Two teenagers arrested in connection with the murder of journalist Lyra McKee in Derry on Thursday have been released without charge as police in the North made a further appeal for help from the local community.

“We have received very tangible support from the community,” said the senior investigating officer, Detective Superintendent Jason Murphy, “but we need to convert this support into tangible evidence that will enable us to bring Lyra’s killers to justice.”

The 29-year-old was shot as she stood with other bystanders watching rioting in the Creggan area of the city on Thursday night. She was taken to hospital in a police vehicle, but died shortly afterwards.

The Police Service of Northern Ireland (PSNI) have said they believe dissident republican group the New IRA was responsible for her murder.

Ms McKee’s funeral will take place in St Anne’s Cathedral in Belfast on Wednesday.

Supt Murphy said that police had already received “unprecedented support” from the local community but he needed to find out if others had been involved.

“Clearly my consideration is whether those two individuals acted in individual or in collusion with other individuals and I’m keen for the community to come forward to help me to answer those questions,” he said.

“Lyra’s family have a lot of questions and I need more help from the community to enable me to answer more of their questions and to bring Lyra’s killers to justice,” he said.

The CCTV footage also shows the gunman at the corner and an individual picking up something from the ground on the same corner.

CCTV footage released by the PSNI appears to show a masked man, dressed in black, pointing a gun from behind cover and firing a number of times towards police and a crowd of onlookers.

A second suspect, dressed in black with light trainers, is then seen crouching at the same spot and reaching towards the ground.

The PSNI released CCTV footage of the Derry riots in which Lyra McKee can be seen circled.

In separate CCTV footage also released by police, Ms McKee can be seen among a crowd of people standing by a police vehicle minutes before she was shot.

Supt Murphy made a specific appeal for anyone who was in the Fanad Drive and Central Drive areas of Creggan on Thursday night and who recorded footage of the riots to come forward to police.

“Please come and speak with my detectives and provide us with your mobile phone footage,” he said.

“We do not need to hold on to your phone, we have necessary equipment that will allow us to download the footage quickly,” he said.

Video footage can also be uploaded to the PSNI’s the major incident public portal at www.mipp.police.uk.

“I know there will be some people who know what happened but are scared to come forward,” he said. “If you have information, no matter how small, please contact detectives.”

Ms McKee’s murder has prompted widespread condemnation in Derry and across the world. Rallies were held in a number of towns and cities in Ireland on Saturday.

Those who have paid tribute to Ms McKee include the former US President, Bill Clinton, who said he was “heartbroken” at her murder and at the violence in Derry.

“The challenges in Northern Ireland today are real,” he said, “but we cannot let go of the last 21 years of hard-won peace and progress.

“This tragedy is a reminder of how much everyone has to lose if we do.”

Journalist Lyra McKee was shot dead overnight during riots in the Creggan area of Derry, Northern Ireland. Photograph: Jess Lowe/AFP/Getty Images

In Derry Bishop Donal McKeown asked mass-goers on Easter Sunday to remember Ms McKee and to pray for all those who are heartbroken at her tragic loss.

At a republican Easter commemoration in Derry’s City Cemetery, Sinn Féin’s Northern leader, Michelle O’Neill, told those responsible for Ms McKee’s murder that they should disband and end their “futile actions”.

“The people who brought guns onto the street, and those who organised them, do not represent any version of Irish republicanism,” she said.

A security alert outside Derry’s main police station and in three other locations in the city yesterday were said by police to be unrelated to Ms McKee’s murder.

Police also said there was no evidence that the presence of production company filming for MTV – which was present when Ms McKee was shot – had exacerbated tensions in the area.

“We are aware that a number of media outlets were present,” a PSNI spokesman said, “and we have asked anyone with footage to supply it to us.”