Amazon Inc. and Walmart Inc.'s plans to dominate India's online retail landscape have been ambushed by Prime Minister Narendra Modi's political priorities heading into a tightening election.

The vote, which must be held by May, has increased the influence of local retailers that lobbied for growth-crimping curbs on the U.S. giants. On cue, India this month rolled out constraints on foreign e-commerce players, including Jeff Bezos-led Amazon and Walmart-owned Flipkart, which together control 70 percent of its online shopping.

The tighter rules, aimed at protecting small traders, may end up benefiting the country's richest man, Mukesh Ambani, who is building a homegrown competitor.