The army has been deployed in three Malawian cities on a second day of anti-government protests in which at least 18 people have been killed.
President Bingu wa Mutharika has vowed to "use any measure I can think of" to quell the demonstrations.
Protesters accuse him of plunging Malawi into its worst economic crisis since independence.
The army has been deployed in the capital, Lilongwe, the biggest city, Blantyre, and Mzuzu in the north.
The troops bolster a strong contingent of riot police in the three cities.
The health ministry said 18 people had been killed in two days of protests, with post-mortems being conducted to establish the cause of death.
"The bodies had fractured bones, deep cuts, broken ribs and lost a lot of blood," health ministry spokesman Henry Chimbali told the AFP news agency.
Nine people died in Mzuzu, six in Lilongwe, two in Blantyre, and one in the town of Karonga on the border with Tanzania, he said.
Another 44 people suffered gunshot wounds in the clashes between protesters and security forces, correspondents say.
A police spokesman said the security forces had opened fire in Lilongwe to prevent shops being looted and cars being smashed.
One bystander was killed when caught in the crossfire, correspondents say.
Lorry-loads of soldiers were patrolling central Lilongwe, clearing barricades set up by protesters.
The city centre is deserted with shops closed, correspondents say.
In an address to the nation, Mr Mutharika said the protesters were "working for Satan" and would be defeated.
"As leader of the country, I have powers vested in me by the constitution to ensure peace, using every measure I can think of," he said.
Rev Maurice Munthali, deputy secretary general of the Church of the Central Africa Presbyterian told the BBC that the nine people who died in Mzuzu had been shot.
"I'm actually in the mortuary identifying the bodies - it's very sad."
Rev Munthali said that some of those in hospital had not been demonstrating but were caught in crossfire.
Police spokeswoman Norah Chimwala confirmed one death and more than 10 gunshot injuries.
She could not confirm if the police had caused the death.
Civil groups which organised the nationwide protests said Malawi was facing a "series of catastrophes".
The cost of living was rising and the country was facing acute shortages of fuel, electricity and foreign currency, they said in a statement.
"There is cause to believe that the current shortages are the worst in all our 47 years [since independence]," the statement said.
They accused the government of failing to listen to the concerns of people, and they feared Malawi was turning into an "autocratic kleptocracy".
Mr Mutharika - who was elected in 2004 - said he was prepared to enter into dialogue with the opposition but they should stop "sending your boys" on the streets to cause chaos.
"I am asking each one of you, wherever you are, to go back to your homes and stop looting," he said.
"By allowing these people to demonstrate violently, have we solved our problems? Do we have fuel or forex [foreign exchange]? Is this democracy? Not so."
Several buildings and businesses belonging to members of the security forces and government allies have been attacked during the violence.
The government passed an austerity budget recently, raising taxes to reduce dependence on aid.
Last week, the UK cut aid to Malawi after accusing the government of handling the economy badly. Other donors have also reduced aid.
Malawi is one of the poorest countries in the world, with an estimated 75% of the population living on less than $1 (60p) a day.