At least 27 people were wounded, four of them critically, when a powerful explosion rocked the venue of a joint election meeting organised by the seven-party ruling alliance at Birgunj, about 200-km from here, on Wednesday.The explosion took place at Narayani Stadium where more than 10,000 people had assembled in the afternoon. The head of the civil administration of Parsa district was also injured in the blast. In the past one week, this is the fourth time a blast has disrupted the ruling alliance’s joint election meeting. Political parties outside the alliance and members of the international community have said that the law and order situation needs to be reformed if a free and fair election to the Constituent Assembly must take place in April.Officials said at least 2,000 security personnel drawn from the civil police and the armed police force deployed in Birgunj. Although there is no confirmation about who was behind the incident, militant terai outfits opposed to the polls are believed to be behind the incident.