OUAGADOUGOU - An officer in Burkina Faso's presidential guard seized power on Saturday promising to lead the West African country to elections after the resignation of longtime President Blaise Compaore, in an apparent putsch against the military chief of staff.Compaore stepped down on Friday after two days of mass protests against his attempts to change the constitution to extend his 27-year rule. At least three people were killed after protesters stormed the parliament building and set it on fire.Army chief of staff General Honore Traore, a Compaore loyalist, had quickly announced on Friday he would take over the presidency on a transitional basis, but this was rejected by the demonstrators and a number of junior officers.After reports of heavy gunfire near the presidential palace early on Saturday, Lieutenant Colonel Issaac Zida, the operational commander of the elite presidential guard, announced on radio that he was taking power."I assume from today the responsibilities of head of this transition and head of state," Zida said, dressed in military fatigues, in the studio of BF1 television."I salute the memory of the martyrs of this uprising and bow to the sacrifices made by our people."The unfolding crisis was being closely watched by the United States and former colonial power France, which were close military allies of Compaore. Under his rule, Burkina Faso became a key ally in Western operations against al-Qaida-linked groups in West Africa.The events will also be carefully followed by other governments in West and Central Africa, where long-serving leaders are reaching the end of their constitutional terms in several countries, including Benin, Congo Republic and Democratic Republic of Congo.