A senior Libyan official is accusing NATO of intensifying its bombing of the country to lay the groundwork for a rebel advance toward the capital, NATO began airstrikes against Libya in March and is operating under a U.N. mandate to protect civilians.

Deputy Foreign Minister Khaled Kaim said in an interview early on Thursday that the alliance’s increased bombings represent the “final phase” of its air campaign.

But he says the push will fail and that civilians will be the ones to pay the price.

Kaim also says Libyan government forces have evidence that Colombian mercenaries funded by the west and its Gulf Arab allies have joined the rebel fighters trying to advance towards Tripoli from the key western city of Misrata.