Barack Obama has used his first high-profile speech since stepping down as US president to take swipes at "strongman politics" and politicians' disregard for facts.

A clash between residents of communities in southern Mexican state of Oaxaca over a land dispute left at least 13 people dead and another one injured, prosecutors said Tuesday.

The armed attack occurred on Monday afternoon in the Yautepec District in Oaxaca, when several inhabitants of the community of Santa Maria Ecatepec were ambushed by residents of the neighboring town of San Lucas Ixcotepec, according to the state prosecutor's office, Xinhua reported.

Three persons have been killed after two small planes collided mid-air in the US state of Florida, authorities have said.

The accident took place on Tuesday, the Federal Aviation Administration said. The whereabouts of a possible fourth passenger is still unknown, Xinhua news agency reported.

Police in the US have confirmed that the man shot dead in a shootout in Kansas City was the suspect in the killing of Indian student Sharat Koppu, who was from Telangana.

US President Donald Trump is facing a barrage of criticism for defending his Russian counterpart Vladimir Putin over claims of Moscow's interference in the 2016 presidential elections.

At a joint news conference with Putin following their summit in Finland on Monday, Trump refused to denounce the Russian leader for interfering in the presidential campaign and instead contradicted American intelligence agencies, the US media reported on Tuesday.

 Five soldiers were killed and one was injured in a military helicopter crash on Tuesday in South Korea's Pohang city, authorities said.

The chopper crashed at the landing strip of a military unit in Pohang, South Gyeongsang province, at about 4.45 p.m., Xinhua news agency reported.

China has installed an unmanned automatic weather observation station near its border with India in Tibet to support its Army in the event of a live fire conflict with New Delhi.

At least 62 militants were killed in airstrikes in Afghanistan's Kandahar province, a military official said on Tuesday.

"The Army aircraft targeted Taliban hideouts in Maroof district in the past 24 hours during which the militants including a key commander were killed," the official told Xinhua news agency.