By Nga Pham
BBC News, Hanoi
Protesters claim the land belongs historically to the Catholic Church
The Vietnamese government is often embroiled in complex disputes over land rights.
But there is one particular row that is currently making the headlines - pitting the government against the country's strong Catholic Church, and now the Buddhist community as well.
For the whole of January, thousands of Catholics gathered outside the building that served as the Vatican ambassador's residence in Hanoi during the 1950s.
Braving the coldest winter for 40 years, they held vigils and prayers in one of the most visible gatherings in decades.
They had one request - that the site be returned to the Catholic Church.
The last Apostolic delegate was expelled by the Communists in 1959 and, since then, the residence has been used by the local Communist People's Committee for various non-religious purposes, such as weddings, motorbike parking and a gymnasium.
Vietnam's Buddhist community has now entered the standoff as well.
The Buddhist Sangha recently sent a letter to Prime Minister Nguyen Tan Dung saying that it, too, wanted ownership.
The case has highlighted the complexity of land issues in Vietnam, especially where religions are involved.
Protests by Catholics in January alarmed the government
It has also caused considerable alarm to the authorities.
They demanded that the Catholic protesters stop their vigil, and some were prosecuted for "abusing religion to cause public disorder".
In the end, the crowds only dispersed when the Archbishop of Hanoi, Joseph Ngo Quang Kiet, announced that the government had promised to give back the land.
But the issue has still not been resolved - and the land has yet to be returned.
Before the Catholics could show their discontent again, an official letter signed by the Venerable Thich Trung Hau, a leader of the official Buddhist Church, was sent to the prime minister.
The letter said the disputed land was in fact the location of an ancient pagoda - one of the most important heritage sites of Vietnamese Buddhism - which was occupied by the French and given to the Catholic Church in the 19th Century.
It asked the government to "consider the Buddhist Sangha one of the main parties to consult before making any decision" regarding the site.
The letter has sparked an angry reaction from the Catholic community.
Online forums such as the VietCatholic website have been swamped with articles and messages saying that only the Catholic Church has rights to the land that they believe was "given to the Church by history".
Some followers of the outlawed Vietnam Unified Buddhist Church also criticised the state-approved Buddhist Sangha's claim, which they feared would only widen the division between the two religions.
Some are worried the dispute could exacerbate religious divisions
Religious issues have always been considered "sensitive" in this communist country.
But tricky as it is, the claim by the Buddhists could, in reality, help make the government's task simpler.
"With both the Catholic and Buddhist Churches vying for the land, the government can now take the religious nuance off the issue, and treat it as a pure land issue," said one leading cultural expert. "It could come down to basic documentation."
Even straight land disputes, though, are not easy to solve.
Land clearance for industrial development, the confiscation of agricultural land and the lack of fair compensation for farmers have all fuelled a number of large-scale public protests in recent years.
"Land use is one of the most complex and sensitive issues in Vietnam," said Nguyen Duc Thinh, a senior official from the government's Religious Affairs Committee.
"Our policy is to examine all disputes, case by case, in accordance with the government's land law," he said.
Vietnamese law stipulates national ownership over all land, which means that organisations and individuals can only apply for the rights to use land, not own it.
Real estate prices in Vietnam have rocketed during the past decade.
In central Hanoi and Ho Chi Minh City, commercial space can sell for as high as in some of the most expensive cities in the world.
The disputed former Vatican ambassador's residence, covering an area of one hectare, is no doubt of great financial value.
"We have come to recognise that the Hanoi Diocese does indeed need a premise for their activities," said Nguyen Duc Thinh.
But he admitted that, like many land disputes, this one would take time to resolve.