At least 20 persons were killed and several injured on Monday in a suicide car bomb explosion near a police checkpoint in Lashkar Gah city of Afghanistan's Helmand Province, officials said."The bombing that occurred at around mid-day is part of Taliban' s coordinated attack. They are trying to capture the control of the city but our security forces are fighting to push them back," Xinhua news agency quoted an official as saying.Most of those killed were police personnel and the number of deaths is likely to rise as the injured were shifted to several hospitals, the official said."More details would be made public later as investigation is underway to find more facts about the incident," the official said, adding that more than two dozen persons were also injured in the explosion.Earlier on Monday, the Taliban seized control of several security checkpoints after heavy clashes in the eastern districts of the city, 555 km south of Kabul.Helmand, notorious for poppy growing, is also a known Taliban stronghold.