At least 31 people have been killed in an explosion caused by a suicide bomber outside a polling station in Quetta Pakistan.

40 others have been injured in a blast in Balochistan’s Quetta on Wednesday, as voting for Pakistan normal elections was underway.

Five policemen and two children were among the victims of the attack in the city of Quetta and it is feared the death toll could rise as many victims are critically hurt.

Terror group ISIS has claimed responsibility for the explosion.

An administration official in Quetta, Hashim Ghilzai, said that the bomber was trying to enter the polling station. When police tried to stop him he blew himself up.

Quetta is the capital of Balochistan, Pakistan's poorest province, which suffers from terrorists and separatist insurgencies.

It was hit by several bombings during the election campaign including Pakistan's deadliest ever suicide attack earlier this month when a blast by ISIS killed 153 people.

Another attack in Balochistan province earlier on Wednesday left one policeman dead and three wounded when a hand grenade was thrown at a polling station in the village of Koshk, in Khuzdar district.

The military has stationed more than 370,000 personnel across Pakistan to improve security for the election, bolstered by an additional 450,000 police.

Polls close at 6pm and a result is expected overnight, although coalition negotiations could take days.