Somali pirates have hijacked a ship with its 10-member crew on its way to the Somali port of El-Maan.
The Semlow, freed last week, was taking aid for victims of the tsunami
The MV Torgelow was carrying fuel and food to a UN-chartered vessel freed last week by gunmen who had held it and its cargo of food aid for three months.
The ship's owner said he was shocked by the most recent hijacking which took place on Sunday.
The International Maritime Board says there have been at least 20 attacks on ships in Somali waters since March.
It urges ships in the area to stay as far away as possible from the shore.
Somalia has had no functioning national government since 1991 and the country has been divided into fiefdoms run by rival warlords.
Karim Kudrati of the Kenya-based Motaku Shipping Agency said the Sri Lankan captain and the nine Kenyan crew members had volunteered to make the trip.
"I am surprised these people are doing this and especially in the holy month of Ramadan. I think we have to withdraw from this service," he told Kenyan television.
The MV Semlow was finally released last week in a deal brokered between the pirates and a Somali businessman with its rice cargo - intended for Somali victims of the Indian Ocean tsunami - intact.
It had run out of fuel and was waiting in El-Maan for supplies before returning to Mombasa in Kenya.
Authorities at the port said the pirates were not paid and had released the Semlow unconditionally.