The families of 10 Indonesian crew believed taken hostage by Islamic militants in the Philippines face an anxious wait as authorities try to track down their whereabouts.
The crew, believed to be all men, were on a tugboat and barge flying Indonesian flags and carrying 7000 tonnes of coal when their vessels were hijacked last week.
Exactly when and where the boats were overrun is not yet known, only that the owner of the vessels discovered what had happened on March 26 via a call from someone claiming to be from the Abu Sayyaf Group - a band of militants from the southern Philippines.
The hijackers have since contacted the owner twice demanding ransom, Indonesia's foreign ministry spokesman Arrmanatha Nasir said on Tuesday.
It is believed the group has called for a ransom of 50 million Philippine peso for the group or about $A1.43 million.
The group is known for its kidnap-for-ransom and extortion ventures, with the former in particular its main source of funding since its creation in 1991.
It has been linked to numerous kidnappings, including the 2011 hostage taking of Australian Warren Richard Rodwell, released more than 15 months later after a payment of about $A94,000.
Abu Sayyaf has also been tied to larger deadly attacks, including on a wedding in Zamboanga City in the southern Philippines in November 2011 in which three people were killed.
Months earlier five people died when an improvised explosive was detonated outside an elementary school in Jolo, also in the south of the country.
Mr Nasir said the Indonesia's foreign ministry was continuing to communicate and co-ordinate with various people, including the foreign minister of the Philippines.
Youla Lasut, wife of one of the crew told the Indonesian website Kompas he had called her on Sunday to say his boat had been hijacked.
"(He said) mama don't panic, the condition is safe. But please immediately call the company (Patria Maritime Line) so that they immediately pay the ransom (he said)."
The vessels - tugboat Brahma 12 and barge Anand 12 - were on their way from South Kalimantan to Batangas in the southern Philippines when captured.
The abandoned tug has since been found by Philippine authorities.
The barge and the 7000 tonnes of coal remain in the hands of the kidnappers whose location is unknown.
Mr Nasir said the priority was the safety of 10 Indonesians taken hostage.
The Philippine Department of Foreign Affairs told AAP it had "no comment to give at this time".
Patria Maritime Line has been contacted for comment.
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