Morales has been battling with an endemic food crisis, exacerbated by opposition anger over his style of government.
Prices of essential food items and grains have soared in Bolivia and led to shortages. Officials, however, say some of the shortages are artificial and engineered by opponents of the president to embarrass his government.
On Thursday, Morales abandoned a public event as officials warned he could face angry protests over shortages and soaring prices of good items. His planned venue, a popular parade in the mining town of Oruru, commemorates a colonial-era uprising.
Popular pro-democracy protests in Tunisia, Egypt and other parts of the Middle East have put Latin American rulers on guard and Morales, already under pressure the opposition, reacted with caution to reports the parade might become a pretext for violent protests against his rule.
Before Morales was to address the trade union gathering, protesters set off explosives near the site, forcing the presidential party to cut short its visit.
Morales faces opposition on different levels, some of it with little relation to his government and more to do with cultural divisions between the indigenous president and Bolivia's powerful European elite.
Food shortages in Bolivia have prompted officials to accuse government opponents of making the situation worse to get back at the government.
Morales cut short his visit and returned to La Paz after protesters set off explosions close to where he was preparing to give a speech in Oruro, the capital of his home province in western Bolivia.
President spokesman Ivan Canelas called the protesters' actions "shameful provocations." However, trade union demonstrators in Bolivia traditionally set off explosives as part of their protests, which usually pass without incident.
Morales has also come under fire for increasing government intervention in food production. Protesters in Santa Cruz, an opposition stronghold, blocked access to the airport to press their demand for dissolution of a government agency responsible for food production.
Critics say the executive agency isn't helpful when Bolivia is facing severe shortages of food products and rising prices. Accusations of corruption and inefficiency in the agency's dealing have built pressure on the government to handle things differently.
Analysts said the biggest challenge facing Bolivia was separating genuine grievances from complaints aimed mainly at undermining Morales and forcing him out of office.
Morales was elected in December 2005, the first indigenous leader to take on the mantle of leadership. Two and a half years later he increased this majority. In a recall referendum on Aug. 14, 2008, more than two-thirds of voters voted to keep him in office. Morales won presidential elections again in December 2009 with 64 percent of the vote.
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