Two-time Masters champion Jose Maria Olazabal, Robert-Jan Derksen, Alan McLean and Marcel Siem are knotted in fourth place at Golf Club St Leon-Rot. That group trails by one at minus-6.
Ernie Els and three-time European Tour winner this season Miguel Angel Jimenez, are part of a group tied for eighth place. Kariem Baraka and British Masters winner Barry Lane joined Els and Jimenez at 5-under-par 67.
Immelman, 24, opened on the back nine Thursday and promptly birdied five of his first six holes, including a pair of 15-footers at 10 and 11. He added another birdie at the 18th, his ninth to make the turn in the lead at 6 under par.
The South African played steady golf with pars to start his second nine. Immelman birdied the 200-yard, par-3 sixth and parred out to get into the clubhouse with a 65.
'I'm feeling good with my game for a little while now,' said Immelman, who is 53rd in this week's World Ranking. 'I knew it was just a matter of putting it all together and so I've been trying to stay patient. We got off to a great start. The momentum just kept going.'
Havret, the Frenchman who won the Italian Open in 2001, took a different course to his share of first place than did Immelman. Havret only tallied two birdies on his front nine, the back side at St Leon-Rot.
On the front side, Havret opened birdie-birdie-eagle to get within one of the lead. He birdied the par-4 eighth hole to match Immelman atop the leaderboard.
'I think it was definitely the putting and the driving today,' said Havret, who stated his goal is to become one of the top two ranked French players so he can compete in the WGC-World Cup. 'Driving is very important on this course because the rough is very big. You don't have want to miss in the rough. Pitching was very nice, as well, so I made a good score.'
Howell birdied the first, then eagled the par-5 third. He birdied the par-3 sixth and recorded three birdies on his back nine to grab a piece of the lead.
Howell won the 1999 Dubai Desert Classic but has yet to visit the winner's circle since. He has had several injuries over the years, including a broken arm.
'I would like to have done better, obviously,' said Howell, who has three top-20 finishes in his last four starts. 'I am hoping that the reason I haven't is down to the injuries I've sustained.'
Reigning British Open champion Ben Curtis opened with a 4-under-par 68 on Thursday. Adam Scott and Eduardo Romero are part of a logjam tied for 20th at minus-3.
Padraig Harrington, the 2003 champion, carded a 2-under 70 and is tied for 29th. Among the notable players knotted with Harrington five strokes back are 2001 U.S. Open champion Retief Goosen and Darren Clarke.