The threat was the third of its kind since the current spell of blasts across the country began on August 17.

Meanwhile, Jama'atul Mujahideen Bangladesh (JMB) also threatened to kill eight journalists in Gazipur if they brand them as 'terrorists or 'militants' in their reports.

It has issued threats to blow up the office of assistant commissioner of land (AC-Land) in Gazipur and to kill the upazila nirbahi officer (UNO) in Kaliganj upazila of Jhenidah.

Sources said an unknown person called Assistant Private Secretary to the Foreign Minister Ataul Haque at around 1:30pm and made the threat.

The APS informed Foreign Minister M Morshed Khan immediately of the renewed threat.

"Have you heard the news of Gazipur blast today (Thursday)? Now your office will come under attack," the unidentified caller was quoted as saying.

Security at the foreign ministry has been tightened further following the threat.

An official on condition of anonymity told The Daily Star that the news of bomb threat was instantly communicated to the state minister for home and the authorities concerned.

Witnesses said the entry of vehicles and visitors to the ministry has been restricted. Officials said another metal detector will be soon installed at the main gate while the other entrances will remain closed.

Plainclothes policemen were seen rounding every floor and compound of the ministry yesterday.

Meanwhile, the banned Islamist outfit JMB yesterday sent two separate letters to the local journalists of Gazipur asking them to help in establishing Islamic rule.

Khairul Islam of Daily Jugantor first received the letter by post at 3:00pm. In separate letters, JMB also threatened Iqbal Ahamed Sarker of the Manabzamin, Emarat Hossain of Bangladesh Television, Mukul Kumar Mallik of the Sangbad, Nasir Ahmed of NTV, Shamsul Haque of the Prothom Alo, Mustafizur Rahman Titu of the Janakantha and Mujibur Rahman of the Ittefaq.

"As Muslims, we have declared a war to establish the rule of Quran," the letter says. "If you continue making propaganda against us through your newspaper, we will make your parents sonless, children fatherless and wife widow," it adds.

AC-Land in Gazipur yesterday told the journalists that the suicide squad members of the banned JMB yesterday threatened to kill him and other officials and blow up his office.

The unnamed bombers of JMB called the AC-Land within a couple of minutes of the suicide attack in front of Gazipur DC office and issued the threat.

The authorities informed the law enforcers of the threats, prompting deployment of additional forces in and around the office.

Our Kushtia correspondent reports: The banned Islamist outfit JMB in a letter on Wednesday threatened to kill the UNO of Kaliganj upazila in Jhenidah.

The threat incident came to light after UNO Moazzem Hossain filed a case in this connection with Kaliganj Police Station yesterday.

Hand-written and signed by an unnamed JMB leader of the district, the letter was posted from Jhenidah central post office on Monday. It says if the UNO does not follow the directions of the letter he would be killed in a suicide bombing and all offices at upazila complex will be blown up any time.

The letter reads, "We hold sway over the district. Instead of arresting us, you'd better follow our lead. You have to stop all anti-Islamic activities in the upazila including running cinemas, schools and colleges."

"We want to let the government know through you that if we are barred from our activities, we will blow up your office (UNO office) any time."

"This call for jihad is to establish Islamic rule in Bangladesh. Those who do not support us are the enemies of Islam."

In response to the threats, police have stepped up security measures in the upazila headquarters.

Our staff correspondent from Khulna adds: JMB has threatened to bomb the Khulna Zilla School and kill its teachers and students.

Headmistress of the school Maleka Begum told The Daily Star yesterday that the militants had made the threats in a letter she received on October 11. She did not disclose the news earlier as the school has been holding test examinations for SSC. But another letter received recently had prompted her to seek additional security for the school.