* China intensified crackdown on anti-graft campaigners
* EU's Ashton deeply concerned over arrests
BRUSSELS, Aug 28 (Reuters) - The European Union called on China on Wednesday to release one of the country's most prominent rights activists, Xu Zhiyong, telling Beijing to respect international standards on freedom of expression.
Police arrested Xu, who has called for officials to disclose their wealth, last week, raising the stakes in the government's crackdown on anti-graft campaigners.
"The EU calls on the Chinese authorities to respect the right to freedom of expression ... and to release Xu Zhiyong as well as all other activists who have been detained or put under house arrest for peacefully expressing their views," Europe's foreign policy chief Catherine Ashton said in a statement.
Western governments have sparred repeatedly with Beijing over human rights and the United States raised Xu's case this month during its annual rights dialogue with China.
Beijing police arrested Xu on a charge of "gathering a crowd to disturb order in a public place", one of Xu's lawyers said at the time. He was detained last month on the same charge. Before that, he had been under house arrest for three months, with no reason given by the authorities.
China has detained at least 16 activists involved in pushing for asset disclosure by officials, in what rights groups say is a new, coordinated crackdown by the ruling Communist Party against graft campaigners.
Tensions between EU and China worsened in May because of a separate row over Chinese solar panel imports to Europe that threatened to start a trade war.
The solar trade dispute, by far the biggest between China and the EU, was defused in July with a deal to set a minimum price for panels from China. But trade tensions are likely to persist because China is seeking to produce sophisticated products that compete with Europe. (Reporting by Justyna Pawlak; Editing by Alison Williams)