Beijing, Jan. 9 (Reuters): An anonymous Chinese couple has donated $600,000 towards tsunami relief, the biggest of more than $12 million in private donations to the national Red Cross, Xinhua news agency said.

?A couple who refused to give their names made the largest contribution of 5 million yuan ($600,000),? Wang Xiaohua, spokesperson for the Red Cross Society of China, said in an overnight report.

The first $2 million of donations collected from increasingly rich Chinese had been given to Indonesia, Sri Lanka, Thailand and Maldives, it said.

?Additional relief materials including medicine, pure water and clothes will be airlifted to the disaster-hit countries soon,? he said.

Chinese Premier Wen Jiabao, responding to an appeal by the UN, has offered an additional $20 million in aid for tsunami-ravaged countries on top of $63 million already pledged.