The text messages received by the Mumbai police threatening a "26/11-like" attack in Mumbai came from a phone number that carried the country code of Pakistan, city Police Commissioner Vivek Phansalkar said on Saturday.

Addressing a press conference here, he said that after receiving the messages, the state Anti-Terrorism Squad (ATS) and the city police personnel have been put on alert.

"Police received messages around 11.30 pm on Friday, which threatened that a 26/11-like attack would be carried out in Mumbai and the city would be blown up. There was a mention of 26/11 attacks terrorist Ajmal Kasab and (deceased) Al Qaeda leader Ayman al-Zawahiri in the messages," he said.

"It was also mentioned that some of their aides are working in India. Prima facie, the threat messages came from a number that has the country code of Pakistan," Phansalkar said.

Police have taken the messages seriously, he said while assuring that citizens' safety and security was their responsibility.

"Necessary measures are being taken to investigate the threat messages. We are alert on coastal security and are coordinating with the Coast Guard," he added.

'Sagar Kavach' operation has been launched and coastal security been beefed up, the police commissioner said.

Process to register the first information report (FIR) at Worli police station in on, Phansalkar said.

Earlier in the day, a city police official said that the text messages were received on the WhatsApp number of the Mumbai traffic police's helpline operated from its control room located at Worli.

One of the messages said that six people will execute the attack, while another mentioned that preparations were on to blow up Mumbai, which would revive the memories of the 26/11 attacks, he said.

In one of the most horrific terrorist attacks in the country's history, 166 people were killed and more than 300 other injured as 10 heavily-armed terrorists from Pakistan created mayhem in Mumbai on November 26, 2008.

The threat messages were received a day after a yacht was found off the Raigad coast near Mumbai with AK-47 rifles and live rounds on board, causing a scare, although officials maintained that there was no terror angle in it.