Acts of ocean piracy rose 20 percent in the first quarter of this year, with waters off Nigeria emerging as the worst pirate hotspot, a watchdog said yesterday.

The International Maritime Bureau (IMB) said in its quarterly report that there were 49 attacks on shipping globally in the first three months of 2008, up from 41 in the same 2007 period.

Merchant shipping carries more than 90 percent of the world's traded goods by volume.