The US used to be the one doing those things. Now it's China.

A visit by Zimbabwean army commander Constantino Chiwenga to China would not normally be seen as unusual, given Beijing's status as Zimbabwe's largest foreign investor and longtime ally.

But days after Chiwenga returned from a recent trip to meet senior Chinese military leaders, Harare was plunged into political chaos as the Zimbabwean military -- led by Chiwenga -- seized control and placed President Robert Mugabe under house arrest.

In that context, Chiwenga's visit to China has come under scrutiny, with speculation that he had sought Beijing's tacit approval for a possible move against Mugabe.

In 2015 alone, Chinese investment topped $450 million, accounting for more than half of all foreign investment into Zimbabwe.

In January this year, Mugabe met with Chinese President Xi Jinping, where he was told by Xi, "China will never forget its old friend." But writing in the influential state media tabloid Global Times on Friday, Wang Hongyi, an associate research fellow at the Institute of West-Asian and African Studies, said concerns had begun to grow over the long-term safety of Beijing's investment in its African partner.

"Chinese investment in Zimbabwe has also fallen victim to Mugabe's policy and some projects were forced to close down or move to other countries in recent years, bringing huge losses," said Wang. "Bilateral cooperation did not realize its potential under Mugabe's rule."