CAMBRIDGE, Mass., March 27 (AP)--The Bangla Desh Association, a newly formed group here that says it represents the Bengali people of East Pakistan, said today it had sent telegrams to President Nixon and to U Thant, the United Nations Secretary general, urging worldwide recognition of the new "Republic of Bangla Desh."

Mohiuddin Alamgir of East Pakistan, now studying for a doctorate in economics at Harvard University, said the telegrams urged immediate intervention in the civil war in East Pakistan and called for a halt to the "genocide being carried out by the West Pakistan Army."

Mr. Alamgir said his group represented about 100 East Pakistanis in the New England Area.