AP Photo

The assassination of Dr Massoud Ali Mohammadi, a Tehran University nuclear physicist, on Tuesday, blamed by the Iranian government on the United States and Israel and their fifth-column allies inside Iran, is the latest sign of an ominous, growing shadow war with Iran over its nuclear standoff with the West.

The US has officially denied any role in the incident in which a remote-controlled bomb attached to a motorbike went off near the 50-year-old professor's home in the Qeytariyeh neighborhood in northern Tehran.