An Indian court rejected on Tuesday an appeal against last month's arrest of key opposition leader and Delhi Chief Minister Arvind Kejriwal in a graft case, an order that comes as a disappointment to the opposition ten days before general elections.

Kejriwal was arrested by financial crime-fighting agency Enforcement Directorate (ED) on March 21 in connection with corruption allegations related to Delhi's liquor policy, sparking protests in the capital and the northern state of Punjab, also governed by his Aam Aadmi Party (AAP).

A city court last week extended Kejriwal's detention until April 15 and moved him to Delhi's Tihar jail, where two senior AAP leaders are also held in the same case. A third AAP leader detained in the case was given bail this month after being imprisoned for six months.

AAP says Kejriwal's arrest in the "fabricated" case is an attempt by Prime Minister Narendra Modi's Bharatiya Janata Party (BJP) government to prevent the high-profile leader from campaigning in the nearly seven-week elections which begin on April 19.

The government and BJP have denied the allegations.

An alliance of 27 opposition parties called 'INDIA', of which AAP is a member, has thrown its weight behind Kejriwal, criticising ED and other federal agencies for what it says is their "politically motivated" investigations.

India's main opposition Congress has accused Modi's government of "tax terrorism", saying the tax department was seeking to cripple it financially through huge tax demands just before elections.

The action against opposition groups is aimed at denying them a level playing field, the INDIA alliance says.

The government denies the accusations and says enforcement agencies are only doing their job by pursuing violations. (Reporting by Sakshi Dayal; Editing by YP Rajesh)