Cars were stopped and searched near the eastern Ukrainian city of Lisichansk yesterday. Ukraine's army seized control of part of the MH17 site, insurgents said. (Getty)  For the second day running Australian and Dutch unarmed police have been forced to turn around before reaching the MH17 crash site due to heavy shelling in eastern Ukraine.  And for the second day running Foreign Minister Julie Bishop has insisted Canberra won't be deterred by the setback.  "Tomorrow we will attempt to make the journey again because we owe it to the families of the people who were killed in this aircraft crash to retrieve the bodies and remains of their loved ones," Ms Bishop told reporters in Kiev on Monday.  "We will not put our police in harm's way, we will not take any unnecessary risks.  "But we will not be deterred in our efforts to get onto that site and retrieve the bodies of Australians who were killed."  The Ukrainian military on Monday said its troops had battled their way into to a string of towns around the scene.  Rebel leaders confirmed they'd lost ground and lashed out at Kiev for pursuing an offensive despite the planned visit by international experts.  Ms Bishop and special envoy Angus Houston met with Ukrainian president Petro Poroshenko on Monday.  The foreign minister said he "reaffirmed his commitment to ensure there was an exclusion zone" around the site.  "And we are seeking to have assurances that there would be a humanitarian corridor," Ms Bishop added.  The minister was then asked whether Mr Poroshenko could be taken at his word given Monday's shelling.  "The (Ukrainian) president can only give assurances on behalf of the Ukrainian military not on behalf of the others," she said, adding there were different separatist groups involved in the conflict, some of which were internally divided.  Meanwhile, Ms Bishop still wants the Ukrainian parliament to ratify a deployment agreement she's signed with her counterpart, Pavlo Klimkin, that would allow Australia to send in armed police or soldiers.  The Dutch now have a similar deal they're hoping to have ratified on Thursday too.  "It's contingency planning," Ms Bishop said.  "This agreement ... sets out the conduct that can be carried on, immunities, privileges and day-today engagement.  "Part of that is to have the right, should it ever be necessary, to bring arms into the country for self defence."  Canberra doesn't envisage that happening, Ms Bishop said, "but it would be reckless not to include it in this kind of agreement".  Do you have any news photos or videos?
Australian and Dutch experts have again been prevented from accessing the MH17 crash site where they want to search for any remaining victims.