The request of the of the EU had earlier been sent by the External Affairs Ministry to the Chhattisgarh government, which had in turn, referred the matter to the High Court.
When Sen`s appeal came up for hearing, a division bench comprising justices T P Sharma and R L Jhanwar, considered the reference on the EU proposal made to it by the state government and decided to allow the eight-member team to witness the proceedings.
Earlier, activists of BJP`s students` wing ABVP protested against the EU team`s visit and showed black flags, prompting the authorities to step up security.
According to the EU, it had earlier informed the MEA that it intended to send representatives from its Delhi-based missions of Belgium, Denmark, Germany, France, Hungary, Sweden, the UK, and the EU, to attend the court hearing.
"The EU has also expressed to the Indian authorities its concern about the conditions pertaining to the detention of Sen," it had said in a statement.
61-year-old Sen, a paediatrician by profession, was convicted for sedition and sentenced to life in prison along with Naxal ideologue Narayan Sanyal and Kolkata businessman Piyush Guha for colluding with Maoists to establish a network to fight the state.
Sen has already challenged in Chhattisgarh High Court the life sentence given to him by a local court.
Officials in Raipur had said yesterday that the request of the EU, which was referred to the state government by the MEA, has been sent to the high court as the authorities felt that it was up to the judges to take a view on it when the appeal of Sen came up for hearing.
They had said the Centre has not issued any directive to the state government on the matter.
Additional Advocate General Kishore Bhaduri had said the permission of the court has to be taken to allow presence of foreign nationals at the hearing.
State BJP vice-president Sachchidanand, who is also a lawyer, has criticised the request of the EU saying it was trying the "interfere" in the due process.