The United Nations' food agency has suspended all aid shipments to Somalia after one of its ships was hijacked by pirates off the Somali coast last week.
The WFP is feeding 28,000 people affected by the tsunami
The World Food Programme ship was taking aid to victims of the last December's Indian Ocean tsunami.
The MV Semlow was sailing from the Kenyan port of Mombasa to Bossaso in north-eastern Somalia.
Waters off the Somali coast are among the most dangerous in the world, the International Maritime Boards says.
"We have suspended all shipments of food aid to Somalia due to the insecurity of Somali waters," said a WFP statement.
"The decision will be reviewed depending on the release of the vessel."
WFP provides an average of 3,000 tonnes of aid a month to 275,000 people in Somalia.
The Kenyan government says the crew - eight Kenyans, a Tanzanian and their Sri Lankan captain - are safe.
Some 28,000 people who lost their homes and livelihoods when the tsunami struck on 26 December are being fed by the UN.
Somalia is awash with some 60,000 militia men and has been without a functioning national government since 1991, which hampered relief efforts to tsunami victims.
Attempts to relocate a new transitional administration - set up in neighbouring Kenya last year - back home have so far failed.
"The hijackers are asking for $500,000 but we've told them we're just a small boat with relief cargo to feed your Somali people," Inayet Kudrati, director of the Kenya-based Mokatu Shipping Agency which leased the ship to the UN, told Reuters news agency.
Earlier this month, the International Maritime Board warned of a surge in piracy in the region and advised vessels to stay at least 85km away from the lawless coast if possible.
Damage from the tsunami was concentrated on the north-eastern coast of Somali, killing up to 200 people, smashing 2,400 fishing boats and displacing as many as 30,000.