Khalil Ibrahim, leader of the JEM, said: "They are not welcome ... They can never come into our area.
"We oppose them coming because China is not interested in human rights. It is just interested in Sudan's resources. We are calling on them to quit Sudan, especially the petroleum areas."
China has advised Sudan to co-operate with UN efforts to resolve the crisis but remains its largest arms supplier, with sales increasing 25-fold between 2002 and 2005.
Total trade rose 124 per cent in the first half of 2007 compared with 2006.
'Oil for blood'
The JEM attacked a Chinese-controlled oil installation in October, in the central Sudanese region of Kordofan, but Ibrahim declined to comment on whether it would target the engineers.
"I am not saying I will attack them. I will not say I will not attack them. What I am saying is that they are taking our oil for blood," he said.
"China has so far only offered $1 million for displaced Darfur people. Meanwhile they are sucking a million barrels of oil out of Sudan every day. We do not welcome them."
The group has said they would welcome peacekeepers from any country but China.
On Friday however, Omar Hassan al-Bashir, Sudan's president, insisted China and Pakistan were the only non-African countries he would accept.
On Saturday, the widely read Sudan Tribune website said the Chinese units were also opposed by Darfur's displaced people.
Hussein Abusharati, spokesman for Darfur Internationally Displaced People, told the Paris-based site that he rejected Beijing's involvement because "genocide and robbery are taking place in Darfur since 2003 thanks to Chinese weapons".
Ali Hamati, a UN spokesman, said the 135 Chinese engineers and medical officers arrived in Nyala at 10.30am (0730 GMT) wearing the blue berets and scarves of UN peacekeepers, the first of a 315-strong contingent promised by Beijing.
The teams will build bridges and roads, and dig wells to prepare the ground for the 26,000 peacekeepers due from January onwards.
The hybrid force is supposed to replace a beleaguered 7,000 strong troop of African Union peacekeepers which is trying to maintain security in Darfur.
Ten AU peacekeepers were killed during a raid on their base in the eastern Darfur town of Haskanita in September.
Ibrahim blamed a breakaway faction of JEM for the attack.
International experts have said the Darfur conflict between the Sudanese government and rebel fighters has killed more than 200,000 people and driven more than 4 million from their homes.
Khartoum, however, has said the international media has exaggerated the scale of the conflict.