The Union Home Ministry on Tuesday issued security alert to all the five states along the Indo-Nepal border in view of political developments in the Himalayan nation.

The Sashastra Seema Bal, the paramilitary force guarding the 1,500-km border, has been asked to keep maximum vigil along the porous boundary to check movement of criminals and flow of arms, a senior Home Ministry official said.

Uttarakhand, Uttar Pradesh, Bihar, West Bengal and Sikkim governments have been told to remain vigilant, he said.

Nepal plunged into a political crisis on Tuesday with Maoists pulling out of the coalition government, dealing a blow to the fragile peace process after their demand for abolition of monarchy was rejected.