Moscow ? A Russian warship Friday rushed to intercept a Ukrainian vessel carrying 33 battle tanks and a hoard of ammunition that was seized by pirates off the Horn of Africa – a bold hijacking that again heightened fears about surging piracy and high-seas terrorism.

A U.S. warship is tracking the vessel, but there has been no decision about intercepting it, U.S. Defense Department officials said.

It was unclear whether the pirates who seized the 530-foot-long cargo ship Faina on Thursday knew what it carried. Still, analysts said it would be extremely difficult to sell such high-profile weaponry like Russian tanks.