Six schools in Delhi received bomb threats through email early on Monday morning, leading to them being closed, PTI reported.

The messages warned of bomb blasts on Friday and Saturday.

This was the second such instance this week. On December 9, more than 40 schools got similar emails, which the police later described as hoaxes.

On Friday, an unidentified Delhi Fire Services official told PTI that calls about bomb threats were received from Bhatnagar International School, Cambridge School, Delhi Public School in Amar Colony, South Delhi Public School, Delhi Police Public School and Venkateshwar Global School.

The fire department, police, bomb detection teams and dog squads were conducting checks at the schools.

The institutions told parents of students not to send them to school, or to pick them up if they had already arrived.

Commenting on the bomb threats, Aam Aadmi Party chief Arvind Kejriwal said that such incidents were “extremely serious and worrying”. He said that such threats would badly affect children and would hamper their studies.

On Monday, a single email with a bomb threat was sent to several schools in the national capital, including Delhi Public School RK Puram, GD Goenka, The British School, The Mother’s International, Modern School, Delhi Public School Vasant Kunj, Delhi Police Public School, Delhi Public School East of Kailash and Salwan Public Schools, among others.

The email claimed that bombs had been placed in the schools. The senders also demanded $30,000, or over Rs 25.4 lakh, in ransom.

After the threats came to light, bomb detection teams, fire officials, local police and dog squads conducted searches at the schools, and the buildings were evacuated.

In the past few months, eight flights at the Delhi airport received hoax bomb threats, as did over 100 hospitals and malls.

Last month, the Delhi High Court directed the government and police to create a standard operating procedure for handling such emergencies.