TV-grab from NDTV shows Pakistani special comandos taking cover in Lahore after gunmen attacked a police training school.[CCTV/AFP/NDTV]

It isn't clear what group might have been behind the attack, which has underscored the growing threat of militancy in Pakistan.

The country is under pressure by the US to battle al-Qaeda and Taliban militants on its own soil.

(CCTV March 31, 2009)