Chief Minister of Gibraltar Fabian Picardo on Sunday sent the Royal Gibraltar Police to intercept Spanish fishing boats protesting at the government’s decision to sink 70 cement blocks in disputed territorial waters where the fishermen have worked.

The demonstration is part of a dispute which began several weeks ago and has triggered a diplomatic incident with Spanish officials increasing border checks on people travelling between “The Rock” and Spain.

Spanish police also attended the hour-long protest in the bay, which both sides claim belong to them, reports La Razón. Gibraltar says it dropped the blocks in order to help develop an artificial reef, but Spain contends it was simply to stop Spanish fishermen from working the area.