Afghan President Ashraf Ghani has accused Pakistan of waging an "undeclared war" on the violence-wracked country.

Ghani, who is attending an international conference on Afghanistan in India, said on Sunday that militants battling the Afghan government forces in Kabul would not have lasted a month had it not been for "sanctuary" provided by Pakistan.

In his address to the conference, the Afghan president said militancy in Afghanistan had significantly increased in 2016. He said Afghanistan suffered its highest number of casualties last year, describing it as an “unacceptable” development.

"Despite our intense engagement with Pakistan on bilateral and multilateral basis, the undeclared war... not only has not abated but also intensified during 2016 with special intensity," Ghani said at the 6th Heart of Asia ministerial conference held in the city of Amritsar.

"One of the key figures in the Taliban movement recently said if they didn't have a sanctuary in Pakistan, they wouldn't last a month," Ghani stated.

Representatives from influential regional countries, including Iran, Pakistan, Russia, and China, as well as global players such as the European Union and United States were among the participants of the conference.

The Heart of Asia organization was founded on November 2, 2011, in the Turkish city of Istanbul.

The conference has focused on finding ways to boost economy and bring peace and stability in Afghanistan, which has been mired in conflict since the US-led invasion of the country in 2001.

Indian Prime Minister Narendra Modi, center right, and high-ranking officials from other countries pose for a group photo at the 6th Heart of Asia ministerial conference in Amritsar, India, December 4, 2016. (Photo by AFP)

Elsewhere in his remarks, the Afghan president said some 30 terrorist organizations, as named by the United Nations, were trying to establish terrorist bases in Afghanistan. Some states are still providing sanctuary or support to these terrorist groups, he said.

Afghan officials have repeatedly accused Pakistan of supporting Taliban.

Renewed violence blamed on Taliban has left many dead in Afghanistan over the past few months. The militants have also been able to threaten several provincial capitals with their offensives.

Relations between Kabul and Islamabad have traditionally been mired in distrust. Afghanistan and Pakistan blame each other for the Taliban violence plaguing both countries.