EC135 Captain reported an NMAC occurred with a regional jet while in cruise flight. The Captain went around and proceeded to land without further incident.

Narrative

While transporting patient to receiving facility; had near miss with regional jet inbound to airport. Cruise flight at 1700 ft. AGL; approximately 120 heading. Checked in with Tower 10 miles out and confirmed Aircraft X status. Cleared to transition Class D and given altimeter; calm winds. At about 7 miles out noticed traffic on [Garmin] GMX display directly on course line and about 700 ft. above. Entered D airspace and noticed target began to move north and descend slightly. Heard Aircraft Y check in with ATC and give them 'Aircraft X traffic' position and instructed them to maintain visual separation. Aircraft Y reported me in sight. ATC then called me and gave 'traffic at 10 o'clock and 3 miles; regional jet; has you in sight. Looked to my 10 [o'clock] and was about to key mic and say 'traffic on TCAS; no visual yet' when I looked around windshield post and saw Aircraft Y closing fast. Simultaneously; aural traffic alert sounded; and I immediately pulled up and banked hard left as right turn would have put me in oncoming path. Crew stated that closest distance in their estimation was 100 yd. Went around Aircraft Y and landed at hospital without further incident. Upon relocation flight back to base; was given a number and asked to call Tower. Notified Company of event and then called Tower. They told me Aircraft Y was being controlled by ZZZ Approach and handed over without much warning. Gave person certificate number and contact info; was told I would get follow up sometime next week.