Indian Prime Minister Manmohan Singh, who was to visit the north eastern state of Assam to open the year-long platinum jubilee celebrations of the state assembly April 7, has postponed his visit due to "unavoidable circumstances" because of a threat from separatist United Liberation Front of Asom (ULFA), according to official sources Thursday.

Security agencies in India's north east state of Assam are prepared for any attempt by the anti-talk faction of ULFA to resort to violence ahead of April 7 which the banned outfit observes as its raising day.

On Wednesday, the central home ministry issued an advisory to the Assam government and neighboring states to be on alert vis-a- vis the ULFA.

The advisory follows inputs that anti-talk faction of ULFA may try to create law and order situation as their leaders have directed their cadres to execute disturbances and disrupt normal life in the region.

Sources in the state government said this will now be held April 20 with the prime minister in attendance.

A senior police officer said, "We have taken all possible precaution to foil any attempt by the militants to create law and order situation ahead of its raising day. Adequate security personnel have been deployed at all strategic points such as oil installations and rail tracks".