MANILA - Automated voting machines were being tested and sealed across the Philippines ahead of Monday's elections as officials rushed to fix a technical problem, with some violence-prone areas placed under special control.

Campaigning ended on Saturday for nearly 18,000 local and national positions, with Senator Benigno "Noynoy" Aquino the favorite to become president after two main opinion polls showed he had a lead of about 20 points over his nearest rivals.

Analysts said Aquino might not win by as much on May 10 as the polls suggested, and could still potentially be overtaken as he lacked the national party organization of his rivals, who are better able to get their supporters out to vote. Former president Joseph Estrada, who was removed from power by an army-backed popular uprising in 2001 and later convicted of plunder before being pardoned, has gained late momentum to catch up with former frontrunner Senator Manny Villar.