(CNN) 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 contro l 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.

China's involvement in Zimbabwe stretches back to the 1970s, when Beijing covertly supplied ammunition and financing to Mugabe's guerrilla forces during the country's war of independence. In the intervening years, China has continued to provide financial and political support to the African nation, investing extensively across a range of sectors and helping to develop key infrastructure projects.

"Since Mugabe took power he has been consistently supported by the Chinese government. China has become the second largest trading partner with Zimbabwe and has invested very largely in the country," said Wang Xinsong, associate professor at Beijing Normal University School of Social Development and Public Policy. China would be very reluctant to see Zimbabwe fall into a period of social instability and political turmoil, he added.

But most observers say there is no way to know how involved China was in the apparent coup, or whether it received advanced warning. Cobus Van Staden, senior researcher on Foreign Policy at the South African Institute of International Affairs, described the possibility as a "billion dollar question."

"The fact there were these kind of visits to Beijing right before (the coup) certainly seems indicative of something, but who knows what that was?"

During Chiwenga's trip to China, he met with Central Military Commission member Gen. Li Zuocheng, according to a Chinese military press release, who told him Zimbabwe and China were "all-weather friends."

He also met with Chinese Defense Minister Gen. Chang Wanquan on November 10 in Beijing.

Chinese Foreign Ministry spokesman Geng Shuang told a press briefing on Thursday the visit was just a "normal military-to-military exchange" which had been planned in advance. "Since the defense ministry hosted him, I don't have other details," he said.

'China will never forget its old friend'

The military ties between the two countries extend beyond mere exchanges, however. According to leaked US diplomatic cables , since independence in 1980, the Zimbabwean government has purchased a range of military hardware from China, "including aircraft, armaments, air defense radars, and medical equipment." In addition, claim the cables, "China regularly sends technical military advisers to work with their Zimbabwean counterparts."

Zimbabwe's recently deposed Vice President Emmerson Mnangagwa, who was fired on November 7 by Mugabe in a move that likely triggered this week's apparent coup, was among the first Zimbabwean Zanu Party guerilla fighters to travel to China for military training

More recently, China has helped finance and construct Zimbabwe's first highly specialized professional military college, Harare's National Defense College

But it is 93-year-old Mugabe, now under house arrest, who has benefited most from China's unwavering support.

As Mugabe's relationship with the West began to deteriorate into the later part of the 1990s, he increasingly looked to his old ally China for economic and political assistance.

Xi shakes hands with Mugabe as he arrives on December 1 in Harare.

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

"China is very loyal in this kind of way, they tend to stand by these long-time allies and every time someone like Mugabe would go to Beijing they'd roll out the red carpet," said Van Staden.

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."

In the opinion piece, Wang said a change of government could be beneficial to China Zimbabwe relations. "Friendly ties will embrace new development opportunities," he said.

'Distant but friendly country'

Official Chinese channels are being more circumspect though, not picking one side over the other.

In a statement released after the apparent coup was under way, a Ministry of Foreign Affairs spokesman said China was "playing close attention" to the situation.

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"We sincerely hope that the situation will remain stable in Zimbabwe and relevant affairs can be handled in a peaceful and proper way," the statement read.

"We will continue to develop friendly cooperation with Zimbabwe following the principle of equal and mutually beneficial cooperation with win-win results."

On Wednesday, an editorial published in the Global Times said no matter what, the Chinese government was unlikely to back down on its close relationship with Zimbabwe.

"China has played a positive and constructive role in Africa. The long-term friendship between China and Zimbabwe will transcend the internal disturbances in Zimbabwe," the editorial said.

"The Chinese public would like to see peace in that distant but friendly country."