The trip by Holy See envoy Leopoldo Girelli is part of efforts to improve long-strained ties between the two states, which have no diplomatic relations.

Girelli presented his letter of credentials issued by Pope Benedict XVI to Archbishop Nguyen Van Nhon, who heads the Catholic church in Vietnam, during a meeting of bishops in HCM City, the church's website said.

Last week in Hanoi the envoy met deputy Foreign minister Bui Thanh Son, who "acknowledged recent encouraging progress in relations with the Vatican," the official Vietnam News Agency (VNA) reported earlier.

On Monday in HCM City the head of the local government held a reception for Girelli, whose visit ends on Sunday, VNA said.

The envoy expressed happiness at his visit, "a historical moment as it was the first time since 1975 the Vietnamese church has an envoy of the pope", the church said in a statement dated Tuesday.

The pontiff in January appointed Girelli as non-resident envoy to Vietnam, which severed diplomatic ties after communist victory reunited the country.

A trip by Vietnamese prime minister Nguyen Tan Dung to the Vatican in 2007 marked a major boost in relations, after regular visits by Vatican cardinals to Vietnam.

Catholic land confiscated since the end of French colonial rule in 1954 remains a contentious issue between the church and state, and has led to demonstrations.

Vietnam has Southeast Asia's largest Roman Catholic community after the Philippines -- about six million among a total population of 86 million.

Religious activity remains under state control.

Agence France Presse - April 28, 2011