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.