"It was attacked at four or five in the morning," Domenico Ievoli, the Naples-based owner of the ship, Marnavi, said, adding that there were 18 people -- seven Indians, six Italians and five Ukrainians -- on board.
"We are in close contact with the Foreign Ministry," he said.
In an emergency notice on its website, the company published a map with the location of the attack and said: "Our vessel Enrico Ievoli has been hijacked."
A foreign ministry spokesman said the Italian Navy had been alerted.
The ship, which measures 138 metres in length, was rescued from a potential hijacking in 2006 after an Italian warship intervened.
Another Italian oil tanker, the Savina Caylyn, was freed on December 21 after more than 10 months in captivity, reportedly after a ransom payment.
In November, the Rosalia D'Amato cargo ship with a crew of 21 was also released after seven months in the hands of Somali pirates.
According to the International Maritime Bureau, there were 352 reported hijackings worldwide between January and September -- more than half of them carried out by Somali pirates, who often operate far from Somalia's shores in the Red Sea or the Indian Ocean.
Rome: Pirates hijacked an Italian chemical and oil tanker with 18 people, including seven Indians, on board at dawn on Tuesday off Oman in an area where Somali pirates operate, officials said.
First Published: Tuesday, December 27, 2011, 17:41