An explosion outside Turkey's interior ministry in the capital, Ankara, was a "terrorist attack", the interior minister has said.
Two attackers arrived in a commercial vehicle around 09:30 (06:30 GMT) and carried out the attack injuring two officers, Ali Yerlikaya said.
Mr Yerlikaya said an attacker blew himself up in front of a ministry building and another was "neutralised".
The explosion happened just hours before parliament was due to reconvene.
It is not clear who the attackers were. No-one has claimed the attack.
A senior Turkish official told Reuters news agency the attackers had hijacked the vehicle and killed its driver in Kayseri, a city 260km (161 miles) south-east of Ankara.
One of the injured officers suffered shrapnel injuries, he added.
The first media reports of an explosion also spoke of gunfire heard in the area. Emergency services rushed to the scene, with police blocking several surrounding roads.
"Our struggle will continue until the last terrorist is neutralised," Mr Yerlikaya wrote on social media.
Ankara police said it was carrying out "controlled explosions" of "suspicious packages" to prevent other explosions.
President Recep Tayyip Erdogan mentioned the attack in his speech during Sunday's opening of parliament: "The attack this morning where two villains were neutralised as a result of the timely intervention of our security units is the final flutters of terrorism.
"The vile people who took aim at the peace and security of our citizens did not reach their goal and they never will."
The Turkish parliament is expected to ratify Sweden's entry into Nato during the autumn session.
Turkey dropped its opposition to Sweden's application in July, having opposed it for months over arguments it hosted Kurdish militants.
Militants, mainly from the banned Kurdish Workers Party, used to carry out frequent attacks across the country.
The group has come under intense pressure by the authorities, who have jailed its leaders and conducted military operations against Kurdish bases inside Turkey and across the border in Syria and Iraq.