The Lebanese authorities must step up their efforts to reveal the fate of thousands of people abducted between 1975 and 1990, during the country's civil war, Amnesty International said.
The organization's call followed the confirmation by DNA test results on Monday that remains recovered last week are those of British journalist Alec Collett, who was 64 when he was seized from a car in Beirut in 1985.
The remains were exhumed by a team of British experts working in co-operation with the Lebanese authorities in the Bekaa Valley, eastern Lebanon. A second body of a younger person was found at the site but not identified.
"The UK government respects its citizens, which is why they sent experts all the way to Lebanon to look for this man," Sawsan Hirbawi, sister of Ahmed Hirbawi who was kidnapped in 1976, told Amnesty International.
"We have been calling on the Lebanese state for so many years to dig up mass graves and reveal the fate of my brother and many others, but our state has done absolutely nothing."
The discovery of Alec Collett's remains shows the inadequacy of steps taken by the Lebanese authorities to reveal the fate and whereabouts of Lebanese, Palestinian and other nationals, abducted by armed militias or subjected to enforced disappearance by Lebanese, Syrian and Israeli forces.
The apparent inability of the Lebanese authorities to identify the second body highlights their failure to establish a database of DNA samples from family members of those who went missing. Associations of families of civil war victims have been campaigning for such a database for more than a decade.
"Europeans are lucky to have governments who care about them and send people to look for them wherever they are," said Samira Zakharia, whose 29-year-old son, Iskandar Zakharia, was kidnapped the same year as Alec Collett.
"But our government does not care. I take 11 pills every day just to keep going in the hope that one day I will know what happened to my son."
Almost 20 years after the end of the civil war, the Lebanese state has generally failed to conduct exhumations at mass graves from the period, even where their presence has been officially acknowledged.
Three of the mass graves are in Beirut and mentioned in a three-page summary of the findings of the Official Commission of Investigation into the Fate of the Abducted and Disappeared Persons in 2000: the St Demetrious Cemetery in Achrafieh, the Martyrs' Cemetery in Horsh Beirut and the English Cemetery in Tahwita.
A preliminary ruling by Lebanese judicial authorities last month, said that the government should provide the full findings of the 2000 investigations. This could lead to exhumations at these sites in the future. The decision came in response to a lawsuit filed by two Lebanese non-governmental organizations.
As far as Amnesty International is aware, the only mass grave where the Lebanese authorities have completed exhumations and DNA tests was next to the Ministry of Defence in al-Yarze. The remains of 24 military personnel were discovered in November 2005, seven months after the withdrawal of Syrian forces from Lebanon. President Michel Suleiman, then the army commander, formed a committee to conduct the DNA tests.
The body of Johnny Nassif, a Lebanese soldier who went missing on 13 October 1990, was the latest to be identified by these tests on 11 November. He was among 10 soldiers said to have been killed during or after clashes with Syrian forces. The remaining 14 bodies belonged to Lebanese soldiers killed in the early to mid 1980s.
The whereabouts of another 20 soldiers and two priests, Albert Sherfan and Suleiman Abu Khalil, who went missing on the same day as Johnny Nassif, remain unknown; their families believe they are being held in Syria.
Amnesty International said that the Lebanese authorities must proceed without delay to investigate all mass grave sites in the country, so that the ordeal of all families waiting for news about relatives missing since the civil war can finally learn the truth about their fate.
Before his death, Alec Collett had been commissioned by the UN Relief and Works Agency (UNRWA) to write about Palestinian refugee camps.
His remains are reported to have been found in the town of Aita al-Foukhar at a site formerly used as a base by Fatah - the Revolutionary Council, a Palestinian militia commonly known as the Abu Nidal Organization. They had claimed responsibility for his kidnapping in 1985 and killing in 1986.
The discovery of the two bodies at the base also raises the possibility that other missing persons could be buried there.
Amnesty International called on the Lebanese authorities to immediately protect the site and take action to check for other human remains.
The organization said that if further bodies are found, the authorities should take steps to identify them and hand them over to their families.