World Bulletin/News Desk

At least six people were killed and 17 wounded by a bomber outside a Shi'ite mosque in the Pakistani city of Rawalpindi on Friday, police said.

The attack took place after a large number of people had gathered in the mosque for a religious event.

"The suicide bomber wanted to enter the (mosque), but blew up at the entrance. He had come on a motorcycle. He went up to the entrance after parking his motorcycle," a wounded security guard told Dawn News television from his hospital bed.

There was no immediate claim of responsibility.

Pakistan has been on high alert for attacks since a Dec. 16 massacre at a school in the city of Peshawar in which at least 145 people, mainly children, were killed.

Shi'ite Muslims make up about a fifth of Pakistan's population of around 180 million. More than 800 Shi'ites have been killed in attacks since the beginning of 2012, according to Human Rights Watch.