KINGSTON (Reuters) - Jamaica declared a curfew and troops patrolled the streets on Sunday as fiercely powerful Hurricane Dean bore down on the island after killing five people earlier on its run through the Caribbean.

Tempers flared in shops where Jamaicans scrambled for last-minute emergency supplies as Dean began to lash the mountainous island with heavy rain. The government opened shelters and urged residents of low-lying areas to evacuate.

The hurricane was an "extremely dangerous" Category 4 storm, the second-highest on the five-step Saffir-Simpson scale, and could strengthen into a rare and potentially catastrophic Category 5 near Mexico's Yucatan Peninsula, the U.S. National Hurricane Center said.