NEW DELHI - At least 11 people were killed in India's eastern state of Bihar due to thunderstorm and rains, officials said Monday.

"Five deaths were reported from Muzzafarpur, six from Patna and Siwan districts," an official told media.

The downpour also disrupted rail traffic between Siwan and Mairwa for few hours.

India's most important weather phenomenon - monsoons (the rainy season) has arrived in India last week. According to Indian Meteorological department, it is likely to reach Bihar by June 20.

The monsoon period which brings about 80 percent of annual rainfall in India begins in June and lasts until September.

Last month 50 people were killed in thunderstorms and cloudbursts in north Indian states of Uttar Pradesh and Uttarakhand.