On Saturday, Lungu had passed through Mongu, 500 km (300 miles) west of the capital Lusaka and his motorcade was obstructed because Hichilema's refused to give way, police said.

They raided Hichilema's house early on Tuesday took him in for questioning.

The two men are old rivals, with Lungu beating Hichilema narrowly in two presidential elections. The Patriotic Front (PF) leader only just won last August's vote, which the opposition United Party for National Development (UPND) says was rigged.

"It has been established that the opposition leader disobeyed police orders to clear the way, thereby putting the life of the head of state in danger," police chief Kakoma Kanganja told reporters.

"We have today jointly charged and arrested Mr Hichilema and five others with treason."

Hichilema's lawyer Jack Mwiimbu said he was waiting for Hichilema to appear in court.

"After that, we are going to take appropriate action in the interest of our client," Mwiimbu told Reuters.

"He is still detained in police cells at Lilayi but he is in high spirits. He has always known that the PF have always wanted to charge him with a non-bailable offence, so he is not shocked," he said.

Zambia's Human Rights Commission (HRC), established under the constitution to investigate human rights violations, said in a statement, that it hoped Hichilema would be treated fairly and brought before the courts of law without unreasonable delay.

Kanganja said the police were acting independently and not under political pressure.

"I wish to reiterate that the actions by the opposition leader were unreasonable, reckless and criminal. Therefore members of the public are being warned that as police we are not going to watch such kind of behaviour by any person, irrespective of their status," he said.

Kanganja said some unnamed people had issued death threats to him and this was under investigation.

Hichilema was granted bail in October after being charged with sedition, a move his team said was an attempt by the ruling party to silence dissent.

Zambia's economy has been depressed for years by low commodity prices, mine closures, rising unemployment, power shortages and soaring food prices that Hichilema blames on mismanagement by Lungu.