Federica Mogherini, the High Representative of the European Union for Foreign Affairs and Security Policy, said the EU was growing increasingly concerned with the situation in the region.
As reported by ABS-CBN, Miss Mogherini said: “We believe that this tension, this militarization, is definitely not conducive to a peaceful environment.”
The EU has joined the US and Australia for calling for freedom of navigation in the South China Sea.
The sea sees one-third of international shipping pass through it carrying over $3trillion (£2.5trillion) in trade.
READ MORE: South China sea news: Fears of total war ERUPT
China has been criticised for building artificial islands within the territory it claims and building military installations.
Miss Mogherini spent eight months as Italy’s Foreign Affairs Minister in the government of Matteo Renzi.
During her time in the role, Mr Renzi visited Beijing and according to South China Morning Post, signed 10 trade agreements with President Xi Jinping.
The European Commission website says it is the biggest trading partner of China.
In 2013, Brussels and Beijing adopted the EU-China 2020 Strategic Agenda for Cooperation.
The EU reaffirmed its support for the One China policy whilst China said it supported EU integration.
No EU member formally recognises Taiwan but UN member in Europe does, the Vatican.
Taipei does have unofficial relations with 20 countries in Europe including the UK and Italy.