European Union naval forces warned that the payment of a reported $5m ransom to free a bulker hijacked by pirates could lead to a new wave of attacks.

The 58,000-dwt Abdullah (built 2015), owned by steel group KSRM, was released at the weekend and the 23 Bangladeshi seafarers freed following the payment, Reuters reported.

In an update, the EU’s Operation Atalanta naval task force, set up to tackle piracy off the Horn of Africa, said there had been a notable surge in incidents that could lead to more piracy attacks off the coast of Somalia.

Since the end of November, up to 18 dhows have been hijacked with up to seven still in the hands of their hijackers.

Operation Atalanta said it had identified several possible pirate camps on the Somali coast with a hotspot north of Eyl where the Abdullah had been at anchorage for several weeks.

“Although there have been no piracy-related incidents in the past seven days, the payment of ransom could create a new wave of dhow hijackings,” the update said.

The dhows are used as motherships that blend with usual traffic and then launch skiffs to attack vessels more than 1,000km off the Somali coast, it said.

“The possibility of attacks in the Gulf of Aden cannot be dismissed. If the targeted vessel cannot repel the attack, pirates may opt to board the ship,” the task force said.

The hijacking in mid-March of the Abdullah, while carrying coal from Dubai to Mozambique, happened more than 1,000km north-east of Mogadishu.

An officer on board sent a message to his wife saying that the 50-strong group of hijackers threatened to kill the crew one by one if they were not paid.