MADRID (Reuters) - Spanish rescue services pulled three drowned men from the Strait of Gibraltar after rescuing one man from a half-sunken, rickety boat and another from the open sea, an emergency services spokeswoman said on Wednesday.

The men are believed to be from a boat that was carrying migrants attempting to cross into Europe, the spokeswoman said. One of the rescued men said there were six people aboard originally, she said.

The search continues for the sixth person. Conditions in the Strait of Gibraltar - a narrow strip of water that connects the Atlantic Ocean to the Mediterranean Sea - are currently dangerous with bad weather and big waves, she said.

Tens of thousands of migrants attempt the treacherous crossing of the Mediterranean Sea from Africa every year in unseaworthy boats, leading to thousands of deaths by drowning.

Migrant drownings have topped 3,000 on Mediterranean Sea routes for the fourth straight year, the International Organization for Migration said on Tuesday.

Migrants seeking a better life in Europe have sought new routes through Spain in an effort to get around European Union actions to curb migration in the central and eastern Mediterranean.

Almost 10,300 people arrived in Spain by sea in the first seven months of 2017, the IOM said in September, four times as many as in 2016.