Mainland companies have financed $26.1 billion by offering offshore bonds so far this year, far more than the total domestic bond financing of $21 billion in the same period, according to the United States-based financial data provider on Tuesday.

Deng Haiqing, chief economist with JZ Securities Co Ltd, said the Chinese government was putting further curbs on capital outflows, and booming outbound mergers and acquisitions could be the main reasons.

The volume and value of outbound M&As by Chinese mainland companies hit a record high in the first three quarters of 2016, a report in November by PricewaterhouseCoopers showed.

Carol Wu, PwC China's transaction services partner, said that given the existing global economic scenario and domestic competitive landscape, mainland companies are increasingly opting for overseas M&As for both diversification and technology upgrading.

Banks and property developers have been the most active participants this year in overseas financing for business expansion.

In February, the Hong Kong arms of Bank of China Ltd and Industrial and Commercial Bank of China Ltd tapped investors for $4 billion in two-year and three-year dollar-denominated deals, while China Construction Bank Corp's European arm raised 500 million euros ($526 million), according to the Financial Times.

Chinese property developers offered almost $3.8 billion bonds overseas in January, creating a seven-month new high, according to data of Bloomberg.

On Feb 14, Road King Infrastructure Ltd issued a $300 million bond and the oversubscription rate was 18 times.

JZ's Deng said: "China has tightened the financing of property developers at home, so these companies are issuing bonds abroad to finance funds."

The China Securities Regulatory Commission said in September that it was stepping up the pace of perfecting the corporate bond requirements in risky sectors such as property.

Last year, the renminbi weakened by 5.8 percent against the dollar in offshore markets and 6.5 percent onshore. So far in 2017, the offshore rate has gained 1.7 percent as the dollar's rally pauses.

The Financial Times quoted C.G. Lai, head of global markets for BNP Paribas Greater China, as saying that there is a combination here of China encouraging borrowing offshore and people making judgments that the depreciation story may not be as severe as they thought.