An explosion has rocked a polling station in the southern Yemeni city of Aden, one day before a vote to replace Ali Abdullah Saleh, the country’s president for more than three decades.
One soldier was killed and another injured as gunfire broke out after the blast on Monday, an official told Reuters news agency.
Witnesses said government troops and armed separatists exchanged fire in the Mansoura neighbourhood of Aden, a stronghold of the movement, where a mass protest against the poll was expected later in the day.
The Southern Movement has called on its supporters to boycott Tuesday's election in which Vice-President Abd Rabbou Mansour al-Hadi will be the only candidate.
A security official said police had carried out "arrest raids on armed hardliners" from the Southern Movement trying "by force to prevent citizens from participating in the elections."
"These elements are trying to create a state of fear among citizens by spreading rumours that February 21 [election day] will see acts of violence," the official told the AFP news agency.
Attacks against electoral offices and polling stations have increased in recent days.
On Sunday night, a rocket-propelled grenade was fired at an election base in the Khour Maksar neighbourhood of Aden, a security official told AFP, adding that there were no casualties.
Three soldiers were also wounded in a clash with southern separatists near a polling booth in the southern Lahij province in the same day.
After a year of protests against Saleh, Yemenis will vote to install Hadi, a 66-year-old career soldier and Saleh’s vice-president since 1994.
Hadi in practice replaced Saleh last June, when the 69-year-old president was wounded in an attack on his presidential compound and then spent more than three months receiving treatment in Saudi Arabia.
Abdullah al-Faqih, a Sanaa-based analyst, said the biggest challenge for Hadi will be to take control of the country's security forces, which remain under the control of Saleh's sons and nephews.
"People are worried about the rule of the military and security institutions in the future," al-Faqih told Al Jazeera.
"They watch closely what happened in Egypt and they are afraid that Hadi will be ruled by the military and not rule the military ... The first challenge is to rebuild the military or at least to remove the leaders so that he can really exercise power in the country."
Tuesday's vote is the result of a power-transition deal brokered by Yemen’s Gulf neighbours in November after months of protests calling for Saleh’s removal.
Saleh is currently undergoing medical treatment in New York, US, and is expected to return to Yemen this week.
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The Gulf-brokered deal gave Saleh and his closest aides immunity from prosecution and made him honorary president.
It also stipulated that Hadi become the next president of Yemen for an interim two-year period.
Nobel peace laureate Tawakkul Karman, an active figure in the uprising, has put her backing behind Hadi, whose image has gone up across the Yemeni capital Sanaa, and said his election would be “the fruit of the popular youth uprising.”
US President Barack Obama on Sunday also voiced support for Hadi.
The one-year uprising has brought much of Yemen to the brink of a major crisis, as analysts fear a civil war if the political situation is not resolved.
The country faces rebellions in both the north and the south, with an al-Qaeda offshoot also responsible for recent attacks in the country.
"If the new government fails to fulfil its obligations to reach out and re-integrate the southerners, the Houthis (northerners) and the youth ... then conflict will be inevitable," political analyst Abdulghani al-Iryani told the Reuters.