Malawi's President Bingu wa Mutharika has vowed to track down the leaders of anti-government protests Wednesday and Thursday that left 18 people dead.

In a speech broadcast on state radio Friday, Mr. Mutharika said attempts to overthrow a legitimate government are treasonous. He named opposition leader John Tembo and Vice President Joyce Banda as suspected organizers.

Also Friday, a mass funeral was held in the northern town of Mzuzu for seven people killed during the protests. Police, fearing more violence, tried unsuccessfully to ban the service.

Troops were patrolling Mzuzu and other major cities Friday.

Amnesty International called for an investigation of the protest deaths and said at least 44 other people, including three children, are being treated for gunshot wounds sustained during the violence.

Reporters Without Borders said at least seven journalists covering the protests were beaten by police. The group said two other reporters were detained. The group also said radio stations were banned from covering the protests.

The protests erupted Wednesday in the country's three largest cities – Mzuzu, Blantyre, and the capital, Lilongwe. Demonstrators said they were protesting bad governance and a weak economy, and called for an end to fuel and currency shortages.

Witnesses say police fired tear gas on rioters who were looting shops. The crackdown has drawn condemnation from the United States, Britain, and the European Union.