Il Nuovo Postiglione - Six missing after building collapses in historic Athens district

The city's mayor Haris Doukas called the blast an "unbelievable disaster" and spoke of the likelihood of an "explosion triggered by... a very significant gas leak" that led to the collapse of the two-storey building at around 7:30 am (0430 GMT) on Friday morning.

The building is just below the Acropolis.

According to the police, the number of missing rose from five to six in the evening.

"Operations are continuing, all the machinery is here, the search will go on throughout the night," said Doukas, who went to the scene.

"These are difficult hours. We stop whenever necessary to keep silent, so we can see if we can hear any sound" made by possible survivors, he added.

According to the public television channel ERT, the missing are a Briton and a Greek woman who lived on the second floor. On the first floor, four American tourists were staying in short-term rental accommodation.

The blast on a small street shook the area, which is normally busy with hundreds of foreign visitors.

The fire service had earlier said they included two elderly people who lived in the building's top floor, and three tourists believed to have rented the apartment below.

Thirty firefighters were deployed with six vehicles as well as three search and rescue dogs, according to the Greek news agency ANA.

Excavators are clearing the rubble and thermal cameras have been deployed at the scene by rescuers, according to images released by AFP.

"The damage extends along the entire street as well as the street behind the building," the mayor said.

- 'Incredible disaster' -

"We are talking about an incredible disaster," he said, adding that two adjoining buildings are in very poor condition.

"Inspections have begun to determine whether they can remain standing or whether they too must be demolished."

Earlier, two women were rescued from an adjacent building and taken to hospital. Another person was slightly injured by debris.

Neighbouring buildings and vehicles parked nearby were damaged.

The owner of the ground floor apartment, Mathaios Artavanis, told the Kathimerini news outlet he had tried to contact "the elderly couple, around 70 years old" without success.

The Plaka district is one of the most touristy areas of Athens.

It is near Hadrian's Arch, one of the main monuments from the Roman period in the Greek capital, where the tourist season continues to be in full swing.

T.Cusumano--INP