CARACAS - Venezuelan President Hugo Chavez appeared headed for victory on Sunday in a referendum on allowing him to remain in power as long as he keeps winning elections, two government-linked sources said, citing exit polls.

Three exit polls showed Chavez won by between six and eight points in a vote where turnout was low, they said.

If confirmed, it would be by far the slimmest victory margin in the career of a man who wants to rule for life.

Most pre-vote opinion surveys predicted a close referendum on the raft of constitutional changes that the opposition and even some long-time former allies say is authoritarian.

But pollsters said a low turnout would favour Chavez, who activated a state-backed get-out-the-vote campaign against an underfunded, fragmented opposition.

If the referendum is approved, Chavez would be able to stay in power as long as he keeps winning elections, control foreign currency reserves, appoint loyalists over regional elected officials and censor the media if he declares an emergency.

Chavez, who has never lost a national vote, had predicted he would win by at least 10 points.

The opposition, which he has soundly defeated in almost yearly votes, had pointed to some pre-vote polls showing it could win.

Foreign investors worry that the loser could contest the result, sparking political turbulence after a campaign marred by violent street clashes.