Sri Lanka's Muttiah Muralitharan said the inexperience of the Zimbabwe batsmen was a key factor in him equalling the world record for wickets taken on the first day of the first Test in Harare on Thursday.

Muralitharan, 32, took six for 45 to reach 519 wickets and equal Courtney Walsh's world mark.

Zimbabwe were dismissed for 199, and Sri Lanka were 67 without loss at the close.

"I think I bowled well because the wicket was not turning very much," Muralitharan told reporters.

"But the inexperience of the batsmen helped me take wickets.

"I didn't think I would get more than a few overs when they were 35 for three."

Zimbabwe were forced to field an inexperienced team, which included five debutants, after 15 experienced players made themselves unavailable in a dispute with the Zimbabwe Cricket Union (ZCU).

The rebels want binding arbitration to resolve their grievances with the ZCU, who have offered mediation, which is not binding.

Muralitharan also passed Australian leg-spinner Shane Warne's total of 517 wickets on Thursday, and said Warne is likely to claim the record when Australia begin their tour of Zimbabwe later this month.

"I think Shane Warne will pass me when Australia come here to Zimbabwe," Muralitharan said.

Muralitharan explained the evolution of the doosra, the controversial delivery that turns away from right-handed batsmen and that has led to allegations that the Sri Lankan transgresses cricket's laws when he bowls it.

"I started working on it about seven years ago, and I haven't bowled it in matches until the last three years because it takes a long time to mature something like that," Muralitharan said.

"You have to be perfect when you bowl at batsmen because spinners bowl so slowly that each loose ball is likely to go for four runs.

"Also, wickets are very flat and firm, and made for batsmen. So bowlers need variety to take wickets."