NAIROBI/GENEVA (Reuters) - Four Ethiopian aid workers employed by two separate foreign organizations were killed in Tigray near the border with Eritrea last month during a war in the northern region, a humanitarian and a diplomatic source said on Wednesday. The circumstances of their deaths were unclear, but they took place in one of four camps for Eritrean refugees, the sources told Reuters. There was no immediate comment from Ethiopia’s government or the Tigray People’s Liberation Front (TPLF) who have been battling since Nov. 4. The aid organizations declined to comment because a communications blackout in Tigray meant relatives had not been reached nor the exact circumstances of their deaths verified. ADVERTISEMENT There were credible but unconfirmed reports that a fifth aid worker had also died in Tigray, another humanitarian source told Reuters in Europe. The conflict is believed to have killed thousands of people in Tigray, sent more than 45,000 refugees fleeing to Sudan, and forced several hundred foreign aid workers to leave the region for safety reasons. Reporting by Nairobi and Geneva newsrooms; Writing by Katharine Houreld; Editing by Andrew Cawthorne and Toby Chopra