A Delhi court extended on Monday the detention of Indian opposition leader Arvind Kejriwal in a graft case until April 23, legal news website Live Law reported, a setback to the opposition which needs him to campaign in general elections that begin this week.

The Enforcement Directorate (ED), India’s financial crime-fighting agency, arrested Kejriwal, the chief minister of Delhi, in a corruption case related to the city’s liquor policy and he had been remanded to custody until April 15.

Kejriwal has challenged his arrest saying it is unlawful and in a separate hearing on Monday, the supreme court of India asked the ED to respond to the challenge in the week of April 29, after which it will hear the case. Kejriwal is a fierce critic of Prime Minister Narendra Modi and rejects the charges against him and other opposition leaders as politically motivated.

Modi and his Bharatiya Janata Party (BJP) deny the accusations and say law enforcement agencies operate independently.

Kejriwal’s March 21 arrest sparked protests in Delhi and the northern state of Punjab, governed by his decade-old Aam Aadmi Party, and drew the attention of the United States and Germany.

His detention has united the 27-party opposition alliance called INDIA, which includes the AAP and the Congress party, but opinion polls suggest that BJP has a strong lead over them and is likely to easily win a historic third term.

India starts voting in a seven-phase general election on April 19. Votes will be counted on June 4.