Tehran, Jan 6 (IANS): Iran has marked a 40-km red zone inside the Iraqi border to thwart any infiltration attempt into its soil by the Islamic State (IS) terrorist group, an Iranian army commander said Tuesday.

The Iranian army has warned the IS militants against any movement towards the Iranian border since the terrorist group has entered Iraq, Xinhua cited Press TV as quoting Ahmad-Reza Pourdastan, commander of the Iranian army's ground forces.

"When IS Takfiri terrorists penetrated western Iraq and were close to the Iranian borders, the ground forces (of Iran's army) were fully ready to annihilate them," the commander said.

"We marked a red line of 40 km into the Iraqi soil and warned (them) that they will face Iran's harsh response if they cross the line," he said.

Pourdastan said that the Iranian army was fully familiar with tactics used by terrorists and closely monitored their movement inside Iraq.

On Monday, media reported that the Iran's border police arrested three people armed with explosives as they tried to cross the country's northwestern border to join IS militants in Iraq.