OUAGADOUGOU, Burkina Faso — Thousands of protesters marched through Burkina Faso's capital Sunday decrying a perceived attempt by the president to extend his hold on power through the creation of a new Senate.

The protest came one week after thousands of workers joined demonstrations around the country against rising costs for basic goods like rice and sugar, underscoring the tense environment facing President Blaise Compaore as he weighs whether to run for re-election in 2015 or step down.

Lawmakers approved the creation of the Senate in May, and on Sunday local officials were selecting 39 members who would represent them in the 89-member body. Compaore will appoint 29 members himself.

Opposition leaders fear Compaore intends to use the Senate to amend Article 37 of the constitution limiting presidents to two five-year terms. Compaore has been in power for 26 years, but his term ends in 2015 and the current rule would not permit him to run again.

"This is huge, the people have gathered in mass, we were not expecting this," said opposition leader and protest organizer Zephirin Diabre after Sunday morning's march and rally in Ouagadougou. "It's proof that the people are rejecting the Senate."

A demonstration was also organized in Bobo-Dioulasso, the country's second-largest city.

Compaore has not said whether he will step down in 2015, and the International Crisis Group warned in a report published last week that this silence was contributing to uncertainty in the country.

In response to last weekend's protests, Prime Minister Luc Adolphe Tiao said the government would begin talks with trade unions over high living costs, but he did not address concerns about the Senate. The talks with unions have not yet begun.

Any attempt by Compaore to change the rules on term limits could invite large-scale demonstrations like those seen in Burkina Faso in the first half of 2011, the International Crisis Group warned in its report.

But with the opposition divided and lacking resources, the report said Compaore is the only actor who can lay the groundwork for a smooth political transition that avoids upheaval should he decide to leave office.