Slumping world markets prompted investors to lock in recent gains on the Athens bourse yesterday, sending the benchmark general index 2.55 percent lower. The Athens bourse’s benchmark index ended at 2,251 points. Banks sustained the heaviest losses, falling 4.45 percent. Index heavyweight National Bank tumbled 5.13 percent to 17.74 euros. Piraeus Bank, which reported below-expected first-quarter data on Wednesday, slipped 4.60 percent to 8.30 euros. World stock markets plunged, as greater job losses in the USA further diminished hopes that the world’s largest economy would soon be growing again and a leading rating agency warned that Britain may face a downgrade to its debt rating. Turnover on the Athens bourse reached 229 million euros versus 307.2 million in the previous session.