Ren Weilian (L) and Zhu Tiantian try on their Chinese imperial-themed wedding outfits in Shagnhai as they prepare for an informal wedding ceremony on a five-day ship cruise

Chatting excitedly as they try on their Chinese imperial-themed wedding outfits, Ren Weilian and Zhu Tiantian are as nervous as any couple as they prepare to exchange vows in their lesbian marriage.

China does not recognise same-sex unions but that's not stopping couples like Ren and Zhu from tying the knot in informal ceremonies as the country's sexual minorities quietly assert their rights.

That push was given a boost when the top court of neighbouring Taiwan last month ruled in favour of legalising same-sex marriage, triggering a surge in online chatter among Chinese gays who hope they, too, can someday legally wed.

"I feel it's quite hard to host a same-sex wedding here because there will be many problems. But I just want us to be able to have our own wedding," said Ren, 26, donning a yellow dress embroidered with phoenix designs.

Couples wave before departing on a cruise from Shanghai to Japan during which they will have an unofficial wedding ceremony, organised by Chinese volunteers from US-founded PFLAG (Parents, Families and Friends of Lesbians and Gays)

Ren and Zhu are among several couples who will unofficially wed aboard a five-day cruise from Shanghai to Japan that left port Wednesday, organised by Chinese volunteers from US-founded PFLAG (Parents, Families and Friends of Lesbians and Gays).

PFLAG will seek to register the same-sex unions in California, which allows them.

"Even though it might not mean much in China, it means a great deal to us," Ren said just before embarking on the cruise.

"At least someone can recognise us."

But many see signs of hope.

LGBT issues are gaining traction in Chinese media and entertainment, and Shanghai's ninth annual gay-pride festival -- China's only one -- is underway, though it is far more tame than its foreign counterparts.

LGBT discourse thrives online and the Chinese gay-dating app Blued claims the world's largest user base, at 27 million, mostly in China.

A court in central China last year ruled against two men who sought legal recognition of their marriage, but the fact that the case was heard was interpreted as a positive step.

But campaigners admit legalisation remains a distant prospect in a country where homosexuality was classified as a mental illness until 2001 and gays still enjoy few rights.

Tens of millions stay in the closet or in sham heterosexual marriages due to parental pressure to produce a male heir.

Zhu herself previously married a man under family pressure. It lasted less than a year.

- Fuelling hopes -

China does not recognise same-sex unions but that's not stopping couples like Ren Weilian (R) and Zhu Tiantian tying the knot in informal ceremonies as the country's sexual minorities quietly assert their rights

"It's definitely very inspiring to see what's happened in Taiwan and fuelled a lot of hopes over here," said James Yang, a UN Development Programme (UNDP) analyst focusing on LGBT issues.

But he noted "fundamental differences" between China and democratic Taiwan, which split decades ago after a civil war.

Official support in Taiwan for gender and LGBT equality is strong, while China lags, Yang said.

China's control-obsessed ruling Communist Party also is extremely wary of giving space to individual communities.

"There's definitely a long way to go. LGBT issues are simply not on the government agenda yet," Yang said.

Many Chinese gays express hope Taiwan will allow them to wed there, but relevant laws remain to be drafted.

Some Chinese gays and lesbians are taking matters into their own hands with discreet wedding ceremonies like the cruise, though they have no legal basis.

Chinese opinion surveys indicate solid majorities, especially among young people, favour gay rights and even same-sex marriage.

- 'Severe consequences' -

But just days after Taiwan's ruling, an LGBT conference in the northwestern city of Xian was abruptly shut down by authorities and several gay activists detained for hours, an organiser told AFP.

Such incidents remain common.

Around the same time, popular Chinese lesbian dating app Rela was also inexplicably closed down.

China still has few openly LGBT organisations and homosexuals outside bigger cities like Beijing and Shanghai risk "severe consequences" including job discrimination and persecution from families and society by coming out, a 2016 UNDP report said.

But the community's profile is steadily rising, said Li Yinhe, a prominent Chinese sociologist and advocate for LGBT rights.

"In the past, homosexuals were underwater. People didn't know they existed. Now they are at least floating on the surface," Li said, while adding it would take more than another decade before legalisation of same-sex unions is even considered.

Shanghai architect Duan Rongfeng and his partner Li Tao took the plunge in 2015, travelling to California to legally wed.

Taiwan's ruling "made us feel this is not far away for the rest of the Chinese world," said Duan, 40.

"Many friends around us are all very confident that China could legalise gay marriage one day. We expect, and look forward to, that day."