NAIROBI, Kenya  Somali pirates have struck again, seizing an oil tanker loaded with $150 million in crude that was headed from Saudi Arabia to the United States, naval authorities said Monday.

According to European naval reports, nine pirates hijacked the tanker and its crew of about 30 about 800 miles offshore and headed back toward pirate havens along the coast of central Somalia. The Somali pirate business appears to be back in full swing after a brief lull this summer that some attributed to increased naval patrols but that may have had more to do with the monsoon season. Now that the seas are calm, the pirates have resumed operations, acting with even greater sophistication.

“They have definitely increased their capacity and their ability to stay out at sea for longer,” said Cyrus Mody, manager of the International Maritime Bureau in London.

The pirates  many of them penniless former fishermen from Somalia’s war zones  appear to be positioning themselves in the middle of the ocean on mother ships and then, for attacks, deploying on motorized dinghies, mere ants compared to the mammoth ships they capture.