Observers have accused authorities of letting their guard amid a period of relative security for shipping companies operating in the strategic route. The hijacking marked the first of its kind since 2012.
Over 20 million are facing famine and starvation in four countries, the UN humanitarian chief has warned. He has urged the Security Council to provide funds and aid access to prevent "these looming human catastrophes."
Armed men seized an oil tanker off the coast of Somalia's northern coast, the EU's anti-piracy mission NAVFOR said late Tuesday.
"Upon receipt of the mayday alert, an EU Naval Force maritime patrol aircraft was launched from its base in Djibouti to overfly the tanker and make radio contact with the ship's master," NAVFOR said in a statement.
"Despite hailing the ship several times, no contact was made and the situation on board remained unclear until late this afternoon," it added. NAVFOR noted that the Somali pirates had demanded ransom, information which they provided to the ship's owner.
Sri Lanka's foreign ministry confirmed an eight-member Sri Lankan crew piloted the Comoros-flagged tanker Aris 13.
The hijacking marks the first of its kind in five years. At their peak in 2011, Somali pirates commandeered several hundred commercial ships costing the global economy an estimated $7 billion (6.6 billion euros), of which 80 percent was borne by the shipping industry.
'Never went away'
The series of hijackings prompted the UN, EU and NATO to intervene patrol maritime routes in and around the Gulf of Aden. However, NATO's mission officially ended in December.
John Steed, director of Oceans Beyond Piracy NGO, said the latest act of piracy off the coast of Somalia showed that the authorities had let their guard down.
"The pirates never went away, they were just doing other forms of crime and if ... ships take risks, the pirates are poised to exploit the weakness," Steed told the Associated Press news agency.
The affected area is considered a strategic trade route that leads through the Suez Canal, linking oilfields of the Middle East with European ports. Modern piracy of the coast of Somalia dates back to 2005.
An intercontinental problem
Attacks on ships by pirates off the Horn of Africa have been declining since Operation Atalanta, a European mission to secure the region's water for shipping, got underway in 2008. But now the problem is on the rise in the Gulf of Guinea. EU leaders are preparing to announce a strategy to increase security efforts in the region.
Piracy spreads west
The International Maritime Bureau in London, which monitors pirate activities, has reported at least 10 incidents in the Gulf of Aden and at least 28 in the Gulf of Guinea in 2013. The number of attacks on the Horn of Africa has been falling steadily: Last year, 75 ships were reported attacked and 237 in 2011. In the Gulf of Guinea, 58 incidents were recorded in 2012, compared to 64 in 2011.
Failed governance in Somalia led to overfishing of its coastline by other countries in the early 1990s. Toxic waste was subsequently dumped in its waters, crippling the local fishing industry. The combination of factors caused some Somalis to resort to piracy, while others later determined it was a good way to make money. Piracy surged in Somali waters in the late 2000s.
Crackdown shows results
Pirate attacks along the Horn of Africa have decreased since the international naval presence there was bolstered. In 2012, 35 ships were attacked by pirates off the coast of Somalia, compared with 163 in 2009. In former piracy hotspots, locals are more concerned about fishing than capturing cargo ships.
On trial in foreign courts
Those captured and accused of piracy can face trial far from their home countries. Where they end up depends on who catches them or the ship they attacked. In 2012, for example, 10 Somalis were sentenced to jail by a Hamburg court for attacking a German-flagged ship. The UN and EU are backing efforts to improve the judicial systems closer to where pirates operate.
Trend toward more violence
West African pirates' methods can be more violent than those off the Horn of Africa. While Somali pirates know they will forfeit ransom if their hostages come to harm, pirates in the west are mainly interested in the oil or valuable cargo on board and less concerned about the people. Their hijacking methods are similar - approaching large vessels out at sea in small craft.
Haves and have-nots
In the West, Nigeria has been exporting oil for the past 20 years, but most of its people have not benefited from the extensive revenues. Almost two-thirds of Nigeria's population lives below the poverty line. To those without livelihoods, the risks of piracy can seem worth it. Political instability and social conflict have left room for pirate gangs to consolidate in the Gulf of Guinea.
No easy fix
While a heavy international military presence was effective in reducing piracy near Somalia, the same solution cannot easily be applied to the Gulf of Guinea. As those countries are sovereign states, their own authorities must work together to find a solution. Still, international interest in finding an answer is high, especially since the region supplies 20 percent of Europe's oil and gas.
Options for a better life
The key to reducing piracy is improving people's lives on land. The challenges are vast - from improving judicial systems to creating a sustainable economy to effectively managing the consequences of natural disasters - like here in a Somali food aid facility where families received rations during a severe drought in 2012.
Author: Samantha Early
ls/bw (AP, AFP, Reuters)