(Adds background on resignation, election)
ALGIERS, March 13 Algerian Prime Minister Abdelmalek Sellal resigned on Thursday, state media said, to run the re-election campaign of President Abdelaziz Bouteflika, the ageing independence leader who is widely expected to win five more years in power.
Bouteflika, 77, registered his candidacy for the April 17 vote last week, one of the few times he has spoken in public since suffering a stroke last year that raised opposition questions about his ability to govern.
Energy Minister Youcef Yousfi will replace Sellal as interim premier, state news agency APS said.
With the support of the ruling National Liberation Front (FLN) party, unions and army factions, Bouteflika is almost assured a win in the North African oil producer and ally in Washington's fight against Islamist militants.
But his low profile since his illness has triggered questions about his health, who would replace him if he is forced to step down and even how he will campaign.
Sellal has said Bouteflika's condition is fine and loyalists see Bouteflika as the man who saved Algeria from its 1990s war with Islamist militants, a conflict that killed around 200,000 people.
But Sellal did little to ease questions about Bouteflika's health when he said this month the president would not need to campaign himself because there were plenty who could do that for him.
Since independence from France in 1962, observers say Algerian politics have been dominated by backroom negotiations among a group of powerful FLN veterans, business leaders and army generals known as "Le Pouvoir" or "The Power" in French.
Several opposition parties have called for a boycott of April's vote because they say Bouteflika's candidacy and the FLN dominance eliminates any fair competition. Other opposition leaders say he is too sick and should step aside.
Any political handover in the key North African energy producer would come a fragile time in the region, still struggling with turmoil that followed the 2011 "Arab Spring" revolts that toppled rulers in Egypt, Tunisia and Libya. (Reporting by Lamine Chikhi; Writing by Patrick Markey; Editing by Andrew Heavens)