ISLAMABAD, July 25 (Xinhua) -- At least 22 people were killed and over 20 others injured in a suicide attack near a polling station in Pakistan's southwest Quetta city on Wednesday, police said.

City police chief said that a suicide bomber riding on a motorcycle attacked a police vehicle near a polling station in the eastern bypass area of Quetta, the provincial capital of the country's southwest Balochistan province.

Police, rescue teams and security forces rushed to the site and shifted the bodies and injured to a hospital.

Hospital officials said the death toll might further rise as several of the injured are in critical condition.

Emergency has been declared in all the hospitals in the city.

Security forces cordoned off the area and kicked off a search operation.

Pakistanis started voting in the country's general elections on Wednesday morning to elect the next central and provincial governments.

Over 180 people, including three candidates, have been killed and over 200 others injured in various terror attacks during the month-long election campaigns in the country.