The mother, who had just returned from work, was informed by the crying girls about the assault after which she informed the police.
The incident comes close on the heels of a similar incident from Dharmadom in Kannur district where a 13-year-old girl had been sexually assaulted by her father, 15-year-old brother and an uncle for nearly two years. All the three have been arrested.
Kerala home minister Thiruvanchoor Radhakrishnan said in Thiruvananthapuram that police had been asked to conduct a thorough probe into both the cases and bring the culprits to book without delay.