Thousands of Christians took part on Saturday in the first mass at Muslim Qatar's only church, opened this week despite threats from Islamists.
Vatican envoy Cardinal Ivan Dias presided over the eucharist attended by around 15,000 worshippers at Our Lady of the Rosary Roman Catholic church in Doha, thanking "God and Qatar for this great gift".
The church, which like elsewhere in the Gulf Arab region has no bells or crosses on its exterior, opened on Friday ahead of western Christianity's celebration of Easter, which this year falls on March 23.
It is the first of five to be constructed in the gas-rich Gulf state.
From early morning, Catholics began arriving at the church, which accommodates around 5,000. Big screens were erected in the grounds to allow the overflow to follow the mass, celebrated during the consecration of the building.
The mass was conducted in English, but prayers were also said in Arabic, Urdu, Hindi, Tagalog, Spanish and French for the many nationalities that would worship in the church.
Dozens of police were deployed around the church, which cost some 20 million dollars (13 million euros), and female officers searched the handbags of women worshippers.
Western embassies, particularly from the United States and Britain, warned nationals living in Qatar to be extra vigilant after an Islamic militants on the Internet made threats linked to the opening of the church.
The US embassy on Thursday released a warning that the new church might be targeted.
"Extremists may elect to use conventional or non-conventional weapons and target both official and private interests. Examples of such targets include ... the new Christian Church complex in Doha," it said.
Worshippers said they were not concerned by the threats.
"It is a day without precedent. I am very happy. The threats were made but I didn't pay them much attention. I trust the country's authorities," Filipino Catholic Shato Mawude told AFP.
Fellow Filipino Ariel Almyede added: "This church is a sign of a possible dialogue between the different faiths."
Qatari Deputy Prime Minister Abdullah bin Hamad al-Attiyah added: "The church sends a positive message to the world ...
"At the moment we are enjoying the construction of mosques and Islamic centres in the West, so we must be fair" toward Christians in the region and allow them places of worship.
Qatar is a close ally of Washington and hosts the command headquarters for US forces in the Middle East.
In the United Arab Emirates (UAE), meanwhile, police were seen on Saturday guarding one of the main churches in bustling Dubai and searching worshippers entering the compound.
Police closed off access to cars around St Mary's Catholic Church and signs were put up in the street directing motorists to park their vehicles in other specified places, an AFP correspondent reported.
A priest who asked not to be named told AFP there had been no threat against the church and the security deployment was a preventive measure. Policemen said the "precautionary" moves would last until March 25, after Easter.
The UAE prides itself on its religious tolerance and cultural diversity, and most Gulf Arab states have long allowed Christians to worship in churches.
But Saudi Arabia, which adheres to a rigorous doctrine of Islam known as Wahhabism and is home to Islam's holiest sites, bans all non-Muslim religious rituals and materials.
However, the papal nuncio in the Gulf, Archbishop Paul-Munjed al-Hashem, said on the sidelines of the Doha mass that talks had begun with Riyadh to convince it to become the final Gulf Arab state to allow churches.
"Discussions are underway with Saudi Arabia to allow the construction of churches in the kingdom," he said, adding that the country had between three and four million Christian residents. "We cannot forecast the outcome."