Greenpeace protesters fighting to save dolphins say they were targeted by trawlers in the English Channel.
The campaigners say flares were fired near Greenpeace inflatables as they tried to stop two UK vessels pair-trawling 32 miles off Devon.
Two divers earlier entered the water with buoys carrying banners saying, "Stop killing dolphins".
Greenpeace says dolphins die in the huge nets strung between the boats as they fish for sea bass.
Niall Bennett, aboard the Greenpeace vessel Esperanza, said the Greenpeace members were about 100 metres away when the flares were fired and missed.
"We are constantly reviewing the situation, safety is paramount," said Mr Bennett, adding that the flares were fired "without warning."
Greenpeace divers and inflatables have been monitoring French and UK trawlers off the Devon coast since 17 February.
On Wednesday divers attached buoys to nets in a bid to force the craft to stop fishing for sea bass.
The UK and French fleets combined could be killing over 2,000 dolphins a year, said Greenpeace.
Sarah Duthie, Greenpeace oceans campaigner on board the Esperanza which is patrolling the Channel, said: "We will attempt to stop as many pair trawlers as possible.
"This destructive form of fishing is killing thousands of dolphins every year."
The UK Government has banned UK pair-trawling within 12 miles of the south-west coast since September 2004.
But Greenpeace wants the ban extended to 200 miles and has mounted a legal challenge in the High Court.
A Defra spokeswoman said fisheries minister Ben Bradshaw had been active in getting the 12-mile exclusion zone, and was seeking to widen it.
Last July Mr Bradshaw called for an emergency closure of the bass fisheries, but this was rejected by France and the European Fisheries Commissioner.
Last March, Mr Bradshaw supported the introduction of observers on fishing boats, which now takes place in the UK.
The spokeswoman said: "The majority of by-catch occurs in international waters, so it is vital for action to take place with the co-operation of our European partners."