Representatives of Canada, India and Ireland joined victims' relatives Thursday in honoring 329 people killed when Air India Flight 182 (search) exploded off the southern Irish coast 20 years ago.

Canadian-based Sikh extremists hostile to the Indian government were blamed for planting a bomb in luggage aboard the aircraft, which was flying from Toronto to Bombay, India. The bomb detonated about 100 miles off the Irish coast on June 23, 1985.

Thursday's ceremony near Bantry, West Cork, began at the moment the plane disappeared from radar — 8:13 a.m. Irish time. More than 200 relatives joined Irish President Mary McAleese and Canadian Prime Minister Paul Martin (search), who both were making their first visits to the annual service.

They all observed a minute's silence at the Air India memorial, a sun dial bearing the names of all 329 dead and the inscription: "Time flies, suns rise and shadows fall, let it pass by, love reigns forever over all."

In a stiff Atlantic breeze, relatives released 329 white balloons into the air. Hindus among the crowd lit incense, chanted prayers and made individual visits to the water's edge, where 331 paper lanterns were set adrift on the ocean tide. The two more lanterns represented two baggage handlers killed the same day by a second bomb that went off in a bag in Toyko's Narita Airport in a parallel attack.

"The tragic, cruel end to the lives of so many men, women and children who left Toronto for Bombay ... was to mark the start of a journey of sorrow for the bereaved," McAleese said.

"We think of them especially on this day, and we hope that in this memorial they may find comfort and solace, for it is a reminder not simply of those lost lives but of continuing care and concern for those who grieve."

At the same podium, spokespeople for the relatives demanded that Canadian authorities establish a public fact-finding inquiry and keep pressing for criminal charges, despite March's acquittal of the two main suspects.

Padmini Turlapati, a doctor from London, Ontario, who lost two sons aged 14 and 11 in the bombing, said relatives of the dead "will not allow your deaths to be in vain. That flame of hope did get a lashing in recent times. ... Our hope will be realized one day."

Martin said Canada would erect its own national memorial, but did not comment on the prospects for an inquiry.

So far only one person has been convicted in the attacks.

In 1991, Inderjit Singh Reyat received a 10-year sentence for his involvement in the bombing that killed the two baggage handlers.

In February 2003, he pleaded guilty to one count of manslaughter relating to the Air India blast and received another five-year term.

Two others accused of planting both bombs — Canadians Ripudaman Singh Malik (search) and Ajaib Singh Bagri (search) — were acquitted in March by the Supreme Court in Vancouver, British Columbia, where investigators believe both bombs originated.