Union Minister Shashi Tharoor's office here was attacked and a motorbike parked in the area damaged on Tuesday allegedly by activists of All India Youth Federation, youth wing of CPI. The Minister of State for HRD, elected to Lok Sabha from Thiruvananthapuram, was not present in the office when the incident happened, Tharoor's office sources said. The attackers came in three autorikshaws and pleted stones and pulled down certain name plates placed in front of the office building, police said. They also damaged the window panes. A case has been registered, police added. No one has been taken into custody in connection with the incident, police said. They said the attack was a sequel to the pelting of stones at District Congress Committee office here last night by AIYF activists. AIFY activists and Youth Congress workers had clashed yesterday in the city during protest marches held by them in support of their positions on the solar scam issue.