BRUSSELS, May 31 (Reuters) - The European Union called for an inquiry into deaths aboard Gaza aid ships seized by Israel's navy on Monday and urged Israel to allow the free flow of humanitarian aid to the Gaza Strip.

The EU also called an emergency meeting of member states' envoys to Brussels to discuss the incident, in which at least 10 people were killed after six ships tried to cross Israel's blockade of the Islamist-controlled Palestinian territory.

High Representative Catherine Ashton expresses her deep regret at the news of loss of life and violence and extends her sympathies to families of the dead and wounded, said a spokesperson for Ashton, the EU's foreign policy chief.

On behalf of the European Union she demands a full inquiry about the circumstances in which this happened.

The spokesperson said Ashton reiterated the EU's position regarding Gaza's closure.

The continued policy of closure is unacceptable and politically counter-productive. She calls for an immediate, sustained and unconditional opening of the crossing for the flow of humanitarian aid, commercial goods and persons to and from Gaza, the spokesperson said.

A European Commission spokesman said separately EU ambassadors would meet later on Monday but gave no details.

The EU has a 300 million euro ($367.5 million) aid budget for the Palestinians.

Israel's military said its troops came under gunfire and knife attack during the takeover. The convoy of aid and foreign activists had set off in international waters off Cyprus on Sunday in defiance of the Israeli-led blockade of Gaza and warnings that it would be intercepted.

Israel says food, medicine and medical equipment are allowed in regularly to Gaza. It says an embargo is needed to stop weapons and materials that can be used to produce them from reaching Hamas Islamists.

(Writing by Justyna Pawlak, editing by Timothy Heritage)