Taliban's birthplace of Kandahar province in southern Afghanistan experienced a horrible day on Monday, as two violent incidents claimed the lives of four civilians, while over two dozen others sustained injuries.

In the first incident carried out by NATO-led troops in the morning rush hour, four non-combatants including a woman were killed and 18 others sustained injuries as NATO-led forces opened fire on a passenger bus in Zhari district.

The gruesome incident triggered demonstration and prompted some 300 locals to block the road and call for the arrest and punishment of those responsible for the mishap.

NATO-led troops expressed regret in a statement, saying the ill- fated bus failed to heed to the warning of the soldiers and continued approaching the military convoy.

NATO-led forces have, as a precautionary measure, asked motorists not to get closer to military convoys.

Hours later, three suicide bombers targeted the department of intelligence service of the National Security Directorate (NSD). Nine people including four employees of NSD and five civilians all members of a family were injured in the incident.

Officials in Kandahar blamed the dreadful attack on the enemies of peace, a term used against Taliban militants, but the outfit has yet to make comment.

The situation in Kandahar, the birthplace of Taliban, has been deteriorating since the emanating of reports last month on military preparation to launch a major offensive against militants in their former stronghold.

Afghan and NATO-led forces commanders said that the troops are getting ready to crackdown Taliban hideouts in Kandahar possibly in June to ensure durable peace there.

The militants who are facing enormous pressure in the southern Helmand province since mid February, after losing their bastion in Marjah to security forces, have intensified their activities, mostly in the shape of roadside bombings and suicide attacks.

However, the security forces, as sign of coordination to counter insurgency, have arrested some 20 terrorists elsewhere in the country, including five in Kabul over the past two weeks and recovered suicide vests and explosive devices from their possessions.

Monday's attack in Kandahar will not be the last one, as the Taliban fighters have vowed to speed up attacks against Afghan and the NATO-led forces this year everywhere in the post-Taliban central Asian state.