Venezuelan President Hugo Chavez appeared headed for a narrow win in a referendum on scrapping term limits on his rule, government officials said, but opposition leaders said the vote was too close to call.

Exit polls and early counts by party members showed the race tightening with the anti-US leader ahead by as little as four percentage points, senior government officials said. Three ministers who asked not to be named earlier said the margin was between six and eight points.

Vice President Jorge Rodriguez told reporters the vote was "close". Opposition politicians also said the outcome was tight and questioned the government's data that put Chavez ahead.

"They are trying to create rumors to present themselves as winners, as victors," Andres Velasquez, an opposition leader said. "We want to deny it categorically, emphatically."

If approved, the referendum vote on a raft of reforms would allow Chavez -- in office since 1999 -- to run for reelection indefinitely, control foreign currency reserves, appoint loyalists over regional elected officials and censor the media if he declares an emergency.

Chavez has said he wants to rule for life and turn the major oil exporter into a socialist state.