Southern Afghanistan has seen a fierce battle between Taleban fighters and police, with officials saying more than 40 people were killed.
The fighting erupted in Helmand province where hundreds of British troops are leading security operations.
Violence also broke out earlier in Kandahar, leaving 18 militants and a female Canadian soldier dead.
The attacks came as Canada's parliament narrowly voted to extend the country's combat mission until 2009.
A suicide bomber also attacked a convoy of vehicles in the western city of Herat on Thursday, police said, killing himself and an American national.
"This morning around 0930 a suicide attacker drove his car in to a passing American convoy of supply trucks in the city of Herat," police chief Gen Aayub Salangi told the BBC, adding that one vehicle had been completely destroyed.
The fighting in Helmand began on Wednesday afternoon. A senior security official told the BBC that Taleban commanders contacted the police and taunted them that they had taken control of the town of Musa Qala.
Heavy clashes followed and lasted until the early hours of Thursday. At least 13 Afghan policemen were killed, along with about 30 Taleban fighters, officials said.
"It was the biggest attack [in Helmand] since the fall of the Taleban," provincial governor Amir Mohammad Akhundzada told Reuters news agency.
The Taleban have stepped up attacks in recent months as the Nato-led International Security Assistance Force expands to help the Afghan government with security and reconstruction.
Isaf currently has about 9,000 personnel but plans to build up to about 21,000 troops by November.
Military commanders say the militants are trying to inflict casualties on foreign troops to undermine domestic support for the deployment.
Britain, which is in charge of security in Helmand, already has hundreds of soldiers there and the full complement of 3,300 will be deployed by June.
The Afghan government has welcomed Canada's decision to extend its mission in the country by two years, saying it benefits the Afghan people and the rest of the world.
"We hope the international community, as they've shown in the past, stay committed with us until Afghanistan stands on its own feet," a presidential spokesman told the AFP news agency.
Canadian Prime Minister Stephen Harper's motion to extend the force's deployment by two years passed by 149 votes to 145, despite opposition complaints of being rushed.
Canada currently has 2,300 soldiers in Afghanistan, mainly in the south where the Taleban-led resistance is strong.
The intense parliamentary debate was magnified by the news that Capt Nichola Goddard had been killed in a gun battle with Taleban fighters - the first female Canadian soldier to die in combat since World War II.
She was killed in clashes some 25km (15 miles) west of the southern city of Kandahar, a centre for Taleban insurgents.
Canadian forces said 18 Taleban fighters had been killed and 26 captured.