MUMBAI: India sounded a countrywide terror alert yesterday after serial blasts in two cities killed 47 people over two days and left scores injured.

At least 30 people were detained in connection with the bombings on Saturday in the western city of Ahmedabad. Two persons were killed a day earlier in low-intensity blasts in the southern IT hub of Bangalore.

“The entire nation, including major metro cities in India, have been put on high alert and they have been asked to step up security in vital installations,” a Home Ministry spokesman said in New Delhi.

Within minutes of the bombs going off in Ahmedabad, newspaper offices received an e-mail from a group calling itself Indian Mujahideen. “If you have the courage, stop the bomb blasts. It’s Mumbai’s turn next. We will bomb the Bombay Stock Exchange (BSE) next week,” the e-mail said.

The same group said it carried out bomb attacks that killed 63 people in the western city of Jaipur in May.

The e-mail was sent from an apartment on Palm Beach Road in Navi Mumbai. The apartment is owned by Abhishek Sharma and was rented out to an American national. Police are interrogating Sharma, the American and other residents of the building.

In the e-mail, the group did not mention the bombings in Bangalore and it was not clear if the attacks were connected. The e-mail’s subject line was: “Await 5 minutes for the revenge of Gujarat,” an apparent reference to 2002 riots in the western state.

Bomb squads defused at least three unexploded devices in Ahmedabad yesterday and two more bombs were found in the city of Surat, one of the world’s biggest diamond-polishing centers, located in Gujarat.

Investigators there also seized a car carrying detonators and a liquid that police suspect may be ammonium nitrate, a chemical often used in explosive devices, city police chief R.M.S. Brar told reporters.

President Pratibha Patil expressed her “grief and sorrow” and also “appealed to the people of Ahmedabad to maintain peace and harmony.” Prime Minister Manmohan Singh also appealed for calm.

Gujarat’s right-wing Hindu leader Narendra Modi warned he would not spare the culprits. “The land of Mahatma Gandhi has been bloodied by terrorists whom we shall not spare,” said Modi, the chief minister of the state where India’s independence hero was born.

Modi is a highly controversial figure, who is accused of turning a blind eye to the 2002 Hindu-Muslim riots in Ahmedabad that left an estimated 2,500 people, mostly Muslims, dead.

British Indian Muslims have strongly condemned the blasts. “No one with the slightest human feelings will ever stoop so low as to take innocent lives like this. The perpetrators are worse than animals, devoid of conscience and human values.” Chairman of Council of Indian Muslims-UK (CIM) Munaf Zeena said in a statement.

“We reiterate our demand made on such tragedies before: The Indian government has to institute an independent inquiry and bring the perpetrators to justice without which the recurrence of such catastrophes cannot be stopped.

“We also urge the Indian government to take strong measures to rein in law enforcement agencies and make them stop their witch hunt. No sooner a tragedy occurs than the harassment and arrests of Muslim youths start taking place,” Zeena said.

In New Delhi, police used loudspeakers and distributed leaflets in crowded market places, warning people to watch out for unclaimed baggage and suspicious objects. Police guarded Hindu temples in the eastern city of Kolkata.

In southern Kerala state, police and bomb squads searched sensitive areas and suspended evening shows at the cinemas in the port city of Kochi and the northern towns of Thrissur and Kozhikode.

Sunil Sarsangi, a reporter with the TV9 network in Bangalore, said he received two calls yesterday afternoon from a person who identified himself as a “mujahid” (holy warrior) from Pakistan and said there would be blasts by 7 p.m. in Kerala. The deadline, however, passed off peacefully.

“He spoke in Hindi but did not specify his group’s targets or why it was targeting Kerala. It was an Internet call and the number displayed was 091118809. I asked him where exactly he was calling from and what he was doing but he did not reply,” he told Manorama News channel.

Pakistan denies backing Muslim militants, including those operating in the disputed Himalayan state of Kashmir.

— With input from Muhammad Ashraf