Armed paramilitary policemen patrol near Kunming Railway Station after the knife attack in March. Pic: AP.

BEIJING (AP) — Chinese prosecutors have filed terrorism and murder charges against four people blamed for a knife attack that killed 29 people in a train station in March.

Monday’s announcement comes amid a security crackdown following a series of deadly attacks the communist government blames on Muslim extremists from China’s northwest.

The March 1 attack at the Kunming Railway Station in Yunnan province also injured more than 140 people. Four attackers were shot and killed by security forces at the scene.

The national prosecutor’s office said a woman who was the only survivor among the attackers was charged Monday with murder and taking part in a terror group. Three people who were arrested elsewhere were charged with murder and with leading the terror group.