Second Test, Kolkata, day three (close):
India 643-6 dec v South Africa 296 & 6-0
Dhoni (right) greets team-mate Laxman after reaching his ton
VVS Laxman and Mahendra Dhoni both added unbeaten centuries to give India a huge 347-run first-innings lead in the second Test against South Africa.
Building on a 249-run stand from Virender Sehwag and Sachin Tendulkar on day two, Laxman hit 143 runs while Dhoni finished on 132 not out.
The pair helped extend the lead by 301 runs, with Amit Mishra the only wicket, before India declared on 643-6.
South Africa added six runs without loss before bad light ended play.
The visitors now face a tough task with two days left to play as they look to maintain their 1-0 series lead.
They will look to replicate the efforts of Laxman and Dhoni, who oozed class as their seventh-wicket partnership garnered their 15th and fourth centuries respectively.
But South Africa did have several opportunities to limit their impact and they will not be looking forward to the prospect of a marathon stand in the last two days in Kolkota.
Mishra made a nuisance of himself at the beginning of the day by wracking up 28 runs alongside Laxman. The nightwatchman hit five boundaries and was dropped by Jacques Kallis and Graham Smith before Kallis made amends by taking a catch at slip from a Morne Morkel delivery.
In overcast morning conditions Dhoni was slow to get his innings going, but it was while bowling to Laxman that South Africa had two chances to make another breakthrough.
First, the batsman mistimed a drive and the inside-edge was almost caught by a diving stand-in wicketkeeper AB de Villiers, while another offering was put down by JP Duminy when Laxman was on 48.
That allowed India to go into lunch on 431-6 and Dhoni and Laxman added a further 117 as they piled on the runs.
The pair both reached their respective centuries in the final session, making it only the second time that four Indian batsman have scored 100s in the same innings.
India then extended their lead past the 300 mark when Dhoni hammered Duminy for consecutive sixes before the declaration was made.