Letters threatening terror attacks -- similar to one addressed to France's (search) prime minister -- were received by French embassies in Muslim countries across the globe, officials said Tuesday.

The letters are signed by a previously unknown Islamic group identifying itself as "Servants of Allah the Powerful and Wise." (search

The letters, sent to two Paris newspapers and addressed to Prime Minister Jean-Pierre Raffarin (search), threatened terror attacks against France and French interests, saying the ban on Islamic headscarves in public schools made France an enemy of Islam.

French embassies in Muslim countries in Africa, the Middle East and Asia received the same letter, the officials said. They were sent March 15 from a post office near the Louvre Museum in central Paris.

Authorities have taken the threat seriously. However, Interior Minister Nicolas Sarkozy (search) has said the letters do not resemble typical messages by Islamic extremist groups, and authorities are looking into whether they could have been sent by an extreme-right group masquerading as Islamic militants.

Scientists at a laboratory in the northwest city of Nantes are studying the messages for traces of DNA, the officials said.

France's ban on headscarves and other religious apparel in the classroom -- designed to uphold a tradition of secularism in schools -- is seen by many in the Arab world as anti-Muslim. After being approved in parliament, the measure became law last week. It is to be enforced as of the new school year starting in September.