Afghanistan: Attacks on intelligence forces kill eight
At least four people were killed when a suicide attacker rammed his motorcycle into a bus in the Afghan capital, Kabul, police have told the BBC.
More than 30 others were injured in the powerful blast in the west of the city.
Security sources said the bus was carrying members of the Afghan intelligence agency, the NDS.
Meanwhile a remote-controlled roadside bomb in the eastern province of Kunar killed another Afghan intelligence service officer and three others.
Separately, Nato says five of its soldiers have been killed in attacks. Four were killed in the east, while a fifth died in the south.
Wednesday's suicide blast in Kabul damaged the bus, several other vehicles and the windows of nearby buildings.
The bomber's body and his destroyed motorbike lay next to the bus. The Taliban have said they carried out the attack.
The security forces cordoned off the area, which is near ministries, the Afghan parliament and offices run by foreign companies.
"Some of the wounded are in critical condition and the death toll may rise," Mohammad Zahir, head of Kabul's crime investigation unit, told the Reuters news agency.
President Hamid Karzai issued a statement condemning the blast.
In the explosion in Kunar province, insurgents detonated the roadside bomb as Afghan intelligence officer Col Sahib Zada's car drove by on his way to his office, police told the BBC. His driver and two bodyguards also died.
The BBC's Bilal Sarwary in Kabul says Col Zada was a powerful intelligence chief who had captured dozens of important militant commanders.
Col Zada, who came from Kunar, was the deputy NDS chief of that province and belonged to a powerful tribe there.
Our correspondent says Col Zada was one of the few provincial officials able to defy the security risk and live outside the provincial capital in his village.
Afghan security officials are often the target of bombings and shootings.
Security forces say the insurgents are stepping up attacks on them as US forces prepare to begin reducing troop numbers in the country from July this year.
Wednesday's bombing is the third time security forces have been targeted in Kabul in less than a month. The capital has been largely spared the worst of the attacks, especially since a "ring of steel" was erected in the city before parliamentary elections in September.
Violence in Afghanistan has reached levels not seen since 2001 when the US ousted the Taliban-led government.