BEIJING/TAIPEI (Reuters) - China has condemned a Taiwan government probe into a tiny but passionately pro-China opposition party, the latest flashpoint between Beijing and a self-ruled island it considers its own.

Taiwanese investigators searched the homes of four officials from the New Party, which currently has no members of parliament, on Tuesday on suspicion they had violated the National Security Act.

A New Party delegation, including at least one of those whose homes was raided, party spokesman Wang Ping-chung, visited China last week as part of a scheduled trip to meet China’s policy-making Taiwan Affairs Office.

The New Party has denounced the raids as politically motivated and retribution for their opposition to Taiwan independence and support for union with China.

Taiwanese prosecutors and the government have not given details of what the party members are suspected of. Unlike in China, where the legal system is controlled by the ruling Communist Party, democratic Taiwan has an independent judiciary.

Taiwan media has reported that the case could be linked to that of Chinese citizen Zhou Hongxu, jailed by a Taiwan court in September for breaching national security laws.

Speaking to reporters in Taipei on Wednesday, New Party spokesman Wang Ping-chung said he knew Zhou, and that Zhou had attended party events held in the past.

“In 2014, when I successfully became a representative of the party, he came to an event to offer his support. Later he participated in our organization events so we of course know him.”

In a short statement released late on Tuesday, China’s Taiwan Affairs Office praised the New Party for its stance in opposing Taiwan independence and upholding the “one China” principle, which states that Taiwan is part of China.

“Recently, the Taiwan authorities have shielded and connived with Taiwan independent splittists, and taken various moves to wantonly crack down on and persecute forces and people who uphold peaceful reunification,” it said.

“We strongly condemn this and are paying close attention to developments,” the office said.

The New Party broke off from the Nationalists, who once ruled all of China, in 1993. Defeated Nationalist forces fled to Taiwan in 1949 after losing a civil war with the Communists.

Relations between China and Taiwan have soured since Tsai Ing-wen of the pro-independence Democratic Progressive Party won presidential elections last year. China suspects she wants to push for Taiwan’s formal independence.

Tsai says she wants to maintain peace with China but will defend Taiwan’s security.

The Chinese military has stepped up air force patrols around Taiwan in recent weeks. China has never renounced the use of force to bring what it considers a wayward province under Chinese control.