NAIROBI — Mali’s prime minister was arrested and forced to resign Tuesday by soldiers who orchestrated a military coup in March, bringing fresh turmoil to a West African country struggling with the seizure of its north by Islamist militants linked to Al Qaeda.

The arrest of Prime Minister Cheick Modibo Diarra late Monday as he was preparing to leave for Paris for medical treatment was followed a few hours later by his forced resignation, along with the dissolution of his entire government. A solemn-faced Diarra appeared on national television in the early hours of Tuesday.