NEW DELHI—India's Prime Minister Manmohan Singh has reshuffled his Cabinet in a bid to overhaul his government's image ahead of state and national elections over the next 18 months.

Seven new ministers and several junior ministers took the oath of office Sunday at a brief ceremony to mark the changes aimed at bringing in younger faces into the Cabinet.

The long-awaited Cabinet changes gained urgency after the Congress Party-led coalition government was hit by a wave of corruption scandals. The revamp also filled several vacancies after a key ally opposed to recent economic reforms quit the coalition.

However, Rahul Gandhi, seen as a prime minister-in-waiting, was not part of the new Cabinet. Congress party leaders said he would concentrate on reviving the fortunes of the party before national elections in 2014.