I think they were hit as hard as we were, and their hearts are here for us

NY victims' widow Dorothy Lake

"We have a shared experience and it is real," Robert Bender, head of the American Red Cross of Greater New York, told the crowd. "The only difference between New York and here is the scale. The events were exactly alike."

In Oklahoma, a truck bomb was planted by anti-government militant Timothy McVeigh. Nineteen children at a day-care centre were among the victims.

'Dirty for dirty'

McVeigh was executed in June 2001 for bombing the Murrah building. Accomplice Terry Nichols was given a federal life sentence but faces trial in Oklahoma on 160 state charges of capital murder.

The bombing changed the way America looked at terrorism

The day was also the anniversary of the fiery end of the 1993 Waco siege in which about 80 members of the Branch Davidians religious group died after FBI agents tried to end a 51-day siege by forcing them out of a central Texas compound.

McVeigh said he bombed the Murrah building in retaliation for the raid, giving the federal government "dirty for dirty."

The Oklahoma ceremony was held at the Oklahoma City National Memorial, a commemorative plaza built on the site of the former Murrah building.

After the ceremony, the memorial museum opened a special exhibit called "A Shared Experience" linking the two disasters with photos, stories and belongings of those who died.

Oklahoma: A shared experience in mourning

Among the visitors was Dorothy Lake, whose husband Bill Lake was one of seven New York firefighters who helped in Oklahoma City rescue efforts in 1995 and died in the World Trade Center last September.

"This is their [Oklahoma's] ground zero," she said.

"I think they were hit as hard as we were, and their hearts are here for us."

The display shows photographs that highlight the shared experience of both communities, including pictures of frightened people running from the Murrah building and from the Pentagon, and rescue workers scrambling through the rubble in Oklahoma City and at the World Trade Centre.