A nursing student shot two women to death and killed herself in front of horrified classmates at a college in the southern US state of Louisiana yesterday, police said.

Investigators still did not have a motive for the early morning killings at the Louisiana Technical College in the state capital, Baton Rouge, police spokesman L'Jean McKneely said.

Details such as the names of the victims and the type of weapon used have not yet been released.

Blake Thibodeaux, 20, a drafting student at the college who was in a nearby classroom, said he heard what he initially thought was a door slamming and asked his teacher if he could investigate.

"I ran towards it and was at the door of the classroom when she shot off the last few rounds," he said, adding that the other students streamed in terror out of the room, many crying. Police spent hours at the school gathering witness testimony and in the early afternoon were still not allowing people to enter the campus. Crowds of bystanders quietly milled around across the street.

The shootings came just hours after a gunman killed two police officers and three city officials on Thursday night when he stormed into a city council meeting in a suburb of St. Louis, Missouri. He was later shot dead by police.

Mass shootings are not particularly rare in the US, where the gun-ownership lobby is politically influential and gun control is far less strict than in many countries.

In the worst shooting rampage in modern US history, a student with a history of mental illness killed 32 people at Virginia Tech university in April 2007 before turning one of his guns on himself.

In December, a 19-year-old gunman in Omaha, Nebraska, killed eight people and then himself at a shopping mall. Last Saturday, a man robbing a clothing store outside Chicago shot five women to death.