KABUL (Reuters) - Twin explosions in the center of the Afghan capital of Kabul wounded at least three people on Wednesday, officials said, amid there were conflicting reports about the cause of the blast.

With the city on high alert following Sunday’s deadly attack on a voter registration center that killed around 60 people in the west of the city, the explosions were reported during the evening rush hour as many people were leaving work.

According to security personnel near the site of the explosion, close to a large mosque in the city center, an unknown attacker threw a hand grenade at a police checkpoint before escaping on foot.

However the public health ministry said the explosion was caused by two magnetic bombs and three people were wounded. Police also said a domestic gas bottle had blown up.

The explosion came on the day Islamist Taliban militants announced the start of their annual spring offensive.