Updated

Turkey's ambassador to Gabon says pirates have released an oil tanker hijacked last week off the West African country's coast, leaving its 24-member Indian crew unharmed.

Ahmet Riza Demirer said the Malta-flagged tanker, operated by the Turkish firm Geden Lines, was released in Nigerian waters early Monday after pirates stole an untold amount of crude oil and other oil products.

Security firm AKE said last week's attack constituted "a significant expansion" of the area affected by piracy in the Gulf of Guinea, occurring 200 nautical miles further south than a previous attack in April.

The International Maritime Bureau warned last week of a "worrying surge" of attacks by pirates in the Gulf of Guinea, which it says is now a greater hotspot for piracy than Somalia's coast.