Kane Williamson, newly installed as the world's premier batsman, scored his fourth double century and second in a month as New Zealand forged a commanding first-innings lead over Pakistan in the second Test in Christchurch on Tuesday.

Williamson reached 238 before his marathon innings came to an end three overs before tea, caught in the deep by Shan Masood off Faheem Ashraf.

The New Zealand captain reached the 200-run milestone with a single off Shaheen Afridi from the first ball he faced after the second rain disruption during the middle session on day three.

On the first ball he faced after the first rain stoppage, Williamson was dropped by Azhar Ali when on 177.

It was a rare error from Williamson who had countered every trap set by Pakistan with a range of strokes from silky touches to powerful drives.

He commanded the crease for nine hours 33 minutes after going to the middle in the 20th over.

It continued an amazing home series for the New Zealand captain who has returned scores of 251, 129, 21, and now 200 not out, and has become the third New Zealander to pass 7,000 runs behind Ross Taylor and Stephen Fleming.

The home side declared their first innings at 659/6, taking a massive lead of 362 runs.

Henry Nicholls scored 157 and Daryl Michell reached his maiden century to be 102 not out.

For Pakistan, Shaheen Afridi, Mohammad Abbas and Faheem Ashraf took two wickets each.

Pakistan, in their second innings, were 8/1, at the close of play, with opener Shan Masood (0) already back in the hut.