Islamabad, Jan 9 (IANS): At least 15 people were killed and 26 injured, including six women, when two passenger vans collided and plunged into a ravine in Pakistan's Punjab province Wednesday evening, officials said.

The ill-fated buses collided in Salgiran area, near Muree,a resort, before plunging into the ravine, Geo News quoted police as saying.

According to state media, the passenger vans, carrying over 50 people, collided and fell into a 150- 200 feet deep ravine while passing each other in the area. The accident apparently happened due to the slippery roads caused by light rains, but investigations were going on, Xinhua reported.

The injured comprised 20 men and six women. Nine of them were critically wounded, media reports said citing hospital officials.

Prime Minister Nawaz Sharif expressed grief over the tragic accident and directed the concerned officials to expedite the rescue work while advising traffic officials to formulate a comprehensive traffic plan for the rainy season.

Rescue officials, late in the night, said they were facing problems in their work due to poor visibility and rainy weather. Over 12 ambulances were pressed into service to shift the injured to Islamabad, about 29 km from the accident site.

The Army had been called by the traffic police for help in rescue operation.